So what else affects biofuels’ emissions? Indirect variables of indirect land-use change

There are factors other than what has been described in detail so far that need to be taken into account to allow accurate GHG emissions estimation from biofuels. As mentioned in an earlier post, this includes taking into account whether the biofuel has useful by-products, such as the high-protein material left after bioethanol production, which can be used as animal feed. Matthews et al. (2011) found that it is realistic to increase ethanol output by up to 3 times compared to the present and still avoid the often-expected indirect emissions from having to convert more natural land to agriculture. Such an increase in bioethanol production is said to easily meet the biofuel demand of the US, for example, expected by 2016 (Matthews et al., 2011). Other useful byproducts include materials which can be utilized in plastics and pharmaceuticals manufacture and yeast for human consumption.

Other indirect determinants of GHG emissions from biofuel production include case-specific electricity generating pathways. In Brazil, for instance, 85% of electricity was generated by hydropower in 2009, which is likely to significantly decrease GHG emissions from production (Matthews et al., 2011).

The information in this post therefore adds to the fact that there is great variation in the emissions from biofuels and that the amount of GHG savings or emissions from biofuels should not be generalized.  

Virgin said to use biofuels in aviation sooner than thought

Hello! I know this deviates slightly from the style of my previous posts, but I'd like to introduce something slightly less academic and heavy for once into my blog to give you guys a break!

The Guardian published an article last night publicizing that Branson is keen to use biofuels as aviation fuel as soon as possible. The article uses adjectival phrases containing the buzz-words 'sustainable' and 'renewable' to discribe these future fuels. 'Yey! Virgin Atlantic Airways is going green, I'm going to fly with them in the future', is most likely the expected response from consumers to this statement.

However, at least I and you, my dear reader, now know that biofuels are not all a 'way ahead', nor are they all a 'blind alley' - their environmental, as well as the socio-economic impacts (as Iwill later show) depend on the specifics of where the biofuel comes from and what process it has gone through before becoming a fuel. The origin and lifecycle of Virgin's future 'sustainable' fuels thus determines their actual sustainability and whether Branson's statement is just another marketing strategy.

Should degraded lands be used for biofuel cultivation – Nair et al. (2011)

So far, we have seen the results of Lange (2011), who suggests that the use of degraded lands is likely to have beneficial GHG reduction effects. But in science nothing can definitely be considered to be correct or incorrect, until proven wrong (Castree et al., 2005); so do other studies come to the same conclusions?

To be able to answer this question, the definition of ‘degraded land’ must be compiled. Nair et al. (2011) suggest that this comprises of lands not currently utilized for anthropogenic activities with decreased biodiversity and primary productivity, which often occur due to anthropogenic activities such as overgrazing, poor agricultural management and deforestation. Such conditions, if management is not improved, may lead to detrimental knock-on effects on the environment, such as soil erosion. This means that if managed well, converting to biofuel production may immediately result in an environmental benefit before the GHG emissions are considered; but what about the GHG emissions?

Using this definition, Nair et al. (2011) have found that converting degraded grassland to biofuel crop production, including the often bedevilled oil palm, produces little extra GHG emissions (including carbon dioxide, nitrous oxide and methane), which only tend to be short-term. This means that these emissions will be compensated for in the long-term, resulting in a net GHG saving over time. However, there are some exceptions, where in the case of degraded tropical rainforest conversion, the extra emissions tend to be of unsustainable levels. Additionally, the biofuel crop type matters, with the nitrogen-demanding corn, sugarcane and soybean being unsuitable for growing on degraded lands, as they will require vast amounts of synthetic nitrogen fertilizer, increasing GHG emissions, as explained in previous posts. Non-nitrogen intensive crops, such as jatropha and oil palm, however, are ideal without major addition of fertilizer despite the low soil fertility, thus resulting in net GHG saving.

However, there are a number of problems with the results of the study. Firstly, there is an issue with defining ‘degraded land’. There is no single agreed definition of the term, meaning that previous definitions differed among each other, which would result in highly varied GHG effects calculations of ‘degraded land’ conversion. For example, Dregne and Chou (1994) suggested that degraded lands comprise 3.6 billion ha in arid regions, while Oldeman (1994) calculated this to be 1.9 billion ha globally (Nair et al., 2011). This great variation means that care should be taken to remember that the results of Nair et al. (2011) only apply to their definition of ‘degraded land’. Secondly, it is important to remember that the results of this study describe the GHG emissions from ‘degraded lands’ conversion overall and it is therefore important not to generalise, as spatial and temporal variations exist in soil characteristics, climate and management practices. Thirdly, the authors mention the presence of data gaps on GHG fluxes in areas such as the tropics, making the results less representative of spatial and temporal variations in emissions. Additionally, it is important to remember the ubiquitous problem of uncertainty in some factors, such as the major uncertainty in nitrous oxide emissions (Nair et al., 2011).

In conclusion, although there are some uncertainties, as there are with every model (Castree et al., 2005), conversion of degraded lands to biofuel cultivation is likely to generally have a positive impact on GHG emissions, provided Nair et al.’s (2011) definition of degraded lands is used. However, site-specific evaluations of the precise outcome may be useful. Nonetheless, the results of the study suggesting a promising future for biofuels cultivation on degraded lands in terms of GHG emissions agree with the results of Lange (2011). This is good news, as degraded lands provide a source of land for biofuel cultivation of which there is a shortage at the moment, supposedly without major environmental and socio-economic problems, such as putting pressure on biodiversity and food production. Additionally, under good management biofuels may reduce problems that degraded lands often entail, such as soil erosion, producing further benefit.

Direct land-use change emissions – does conversion of natural lands always contribute to extra GHG emissions compared to fossil fuels? Lange (2011).

As mentioned in my previous post, the conversion of agricultural lands entails major indirect land-use changes and socio-economic consequences, so let’s now consider the effects of converting of natural lands in greater detail.

It may not be surprising that 20% of global GHG emissions arise due to forest degradation and deforestation (Lange, 2011), meaning that if biofuel production entails forest destruction, it is not saving emissions. However, what about the emissions from the conversion of other types of natural habitats? Let's look at this in more detail.

While Mellilo et al. (2009) model uncontrolled future biofuel expansion, Lange (2011), uses a more realistic scenario for the EU by including sustainability regulations, such as the prohibition of converting lands where the indirect emissions are too large to lead to the minimum of 35% emissions reduction compared to fossil fuels (Lange, 2011). While Lange’s (2011) study focuses on EU reduction targets, the results apply to other areas of the world, as the indirect land-use change emissions involve global land-use changes, provided the land-use changes outside the EU are carried out in a similarly controlled manner.

They found that apart from converting savannah grasslands to biofuel cultivation, conversion of other natural vegetation types is unlikely to contribute towards the 35% minimum GHG emissions reduction aim posed by the EU. This means that lands which were previously used for agriculture or other anthropogenic activities and degraded lands are most suitable for biofuel production, producing most GHG emissions reductions.

However, this poses problems such as pressure on the food production industry and on biodiversity, which is often high in these areas despite the low primary productivity (Lange, 2011); these issues will be discussed in more detail later on in the blog. Additionally, due to the market-driven nature of biofuel production, it would be unrealistic not to include the economic factors of using such lands. Incorporating these factors, it seems that it is unlikely that degraded lands will be economically viable to convert under the current policy within the EU, where cultivation subsidies decline with land degradation level. This is especially detrimental when considering that biofuel crop fertility on degraded lands will be lower than on non-degraded, further limiting the economic benefit and thus the potential of degraded lands conversion (Lange, 2011).

In conclusion, according to Lange (2011), when considering just the GHG emissions potential, only some savannah grasslands, brownfield sites and degraded lands could potentially be used for biofuel production. This is therefore in agreement with the suggestion of Mellilo et al. (2009). However, socio-environmental impacts of using these lands need to be considered.  Additionally, taking into account the economic factors, some policy changes need to be made before the use of degraded lands becomes viable.

Indirect land-use change emissions and the GHG effect of biofuels

Searchinger et al. (2008) have found that taking into account indirect land-use change emissions that arise from converting more natural lands to agricultural as a result of biofuels’ displacement of croplands, actually results in major extra GHG emissions compared to fossil fuels. For example, they concluded that the production of ethanol from corn in the US increases GHG emissions relative to fossil fuels for 167 years and double the emissions in the next 30 years, instead of reducing the emissions by 20% as suggested by studies not accounting for indirect land-use changes. Even switchgrass, previously deemed to be particularly GHG-saving, results in 50% increase in emissions in the medium-term, according to Searchinger et al. (2008).

Similarly pessimistic results are obtained by Mellilo et al. (2009), who found that due to the indirect land-use change emissions, greater GHG emissions will result if natural lands conversion is involved (i.e. indirect land-use change), instead of a case where agricultural lands are used more intensely without the extra indirect land-use change emissions. Additionally, the time it takes for the carbon emissions to become favourable is less where no indirect land-use changes are involved, taking 30-50 years on average instead of over 100 years for indirect land-use changes (Table 1). Therefore, due to the major medium-term emissions, the authors suggest that conversion of natural lands will be unfavourable overall, where net GHG saving in the long-term will not compensate for the potential global warming contribution effect caused by the initial indirect emissions. At the same time, a more intensive use of agricultural lands is likely to require so much fertilizer, that this activity may also become unfavourable in terms of nitrous oxide emissions in the longer term. 

Variable       Case 1                                                Case 2

Time period 2000–2030 2000–2050 2000–2100    2000–2030 2000–2050 2000–2100 

Direct land C       11             27                 0                  –52            –24              –7

Indirect land C    190           57                  7                  181             31                1

Fertilizer N₂O      29            28                 20                  30              26                19

Total                    229          112               26                  158             32                13

Table 1. Carbon intensity index using cellulosic biofuels under scenario1 - natural lands are converted to biofuels and scenario 2 - croplands are used more intensively to produce crops and biofuels; in g CO₂eq MJ^–1

If indirect land-use change emissions from natural lands conversion result in unfavourable medium-term emissions and the more intense use of agricultural land results in unfavourable direct emissions, does that mean that biofuels are a blind alley and there is no point in me continuing to write this blog?

Well, fortunately, not all is lost. Firstly, the results of the analysis by Mellilo et al. (2009) only apply to healthy natural lands and to high-value agricultural lands. However, the authors suggest a potentially favourable GHG emissions outcome if using natural degraded lands and low-value lands that were previously utilized for anthropogenic activities, including degraded agricultural areas and lands which have already been deforested.

Secondly, there are some limitations to these studies calculating indirect land-use change emissions. They model uncontrolled biofuel expansion, not accounting for sustainability regulations in the EU such as the prohibition of converting lands where the indirect emissions means emissions reduction is less than 35% compared to fossil fuels (Lange, 2011). Additionally, they attribute 100% of the indirect GHG emissions to biofuels. These limitations make those studies unrealistic, only showing the worst-case scenario.

Should indirect land-use change emissions from biofuel production be attributed to biofuels? A review of Kim et al., 2008

There are two types of land-use change: ‘direct’ and ‘indirect’, the former referring to the removal of previously-growing vegetation together with the carbon it stores within it and replacing it with the biofuel crops. 'Indirect' involves land-use change elsewhere (Mellilo et al., 2009). Indirect land-use change is said to account for twice as many emissions as direct at the present (Mellilo et al., 2009), making it especially important. Some studies suggest that if indirect land-use changes are taken into account, the expected reduction in GHG emissions by substituting fossil fuels with corn ethanol biofuels, for example, becomes negligible (Searchinger et al., 2008), reflecting on the importance of the issue of whether the responsibility of indirect land-use changes should be given to biofuels.

Kim et al. (2008) question whether indirect land-use change should be taken into account in biofuel emissions calculations, or at least how much of the indirect emissions should be attributed to biofuels and who should be blamed for the indirect land-use change emissions. This is because the amount of emissions depends not just on biofuel growers but also on the grower of the crop that would have been grown instead of the biofuel. Would it be fair to attribute all the land-use change emissions to an environmentally-conscious ethanol producer, and not holding the potentially unsustainable activities of those producing land-use changes elsewhere, such as clearing the rainforest to produce soya, responsible for any? Kim et al. (2008) question the universal applicability of the concepts of the ‘polluter pays’ and ‘think globally, act locally’ to biofuels, due to the difficulties that arise in establishing who the polluter is and how to distribute emissions. They illustrate the validity of their belief by showing that at least 70% of crops such as corn grown globally is used as animal feed, meaning that biofuels contribute relatively little to emissions if the bigger picture is taken into account. Additionally, total agricultural emissions account for less than 20% of the total GHG emissions from land-use change, making biofuels seem even less responsible for the impact.

However, I feel that Kim et al. (2008) seem to draw attention away from the impact of biofuels. For example, they suggest that since 90% of all land-use change emissions arise from agriculture, timber and construction industries, biofuels are of little importance here. I, on the other hand, feel that all of these parties should be attributed equal responsibility and that biofuels are thus no less important. Attributing less responsibility to biofuels is potentially encouraging unsustainable practices in their production.

Nonetheless, this is an important point, showing where variations in indirect land-use change calculations may arise even under identical conditions and reminding of the importance of other parties producing land-use emissions. This also demonstrates the problem with most indirect land-use change calculations of biofuels, which usually attribute all the emissions to the biofuel industry, meaning that the calculations suggest worst-case scenarios of biofuels impact. This should thus be kept in mind when evaluating biofuels’ emissions.

My conclusion after reading Kim et al.’s (2008) view is thus that biofuels should be responsible for a part of the emissions to avoid the arguably current overestimation of emissions from biofuels. However, the other often-ignored participants of the land-use change emissions should be given more responsibility than they seem to be at the moment.

Illustrating GHG emissions variations by geographic region and previous land-use

I found a graph created by Stanford University illustrating the variation in cultivation emissions from biofuels in different regions of the US, which is most likely to reflect on variations in soil organic carbon content and climate.

Curtright, 2011

Here is another graph, illustrating the importance of prior landuse and what biofuel it is replaced with (direct land-ue change).

Curtright, 2011

Please note that these are the immediate emissions from the direct land-use change; these emissions decrease with time. This means that while this graph does not show the overall long-term emissions from biofuels, it allows the comparison of GHG emissions from 1st generation biofuels (corn) and second generation biofuels (switchgrass), as well as showing the importance of direct land-use change.

The most surprising aspect shown in this graph is probably the relatively small short-tem emissions from forest conversion. It would perhaps be interesting to know what assumptions were used here i.e. it may be that the emissions from deforestation were attributed to the logging industry instead of to biofuels, producing such low emissions; or whether the wood from deforestation is assumed to be used as a biofuel (although this is not explicitly specified by Curtright, it seems that the latter is the assumption used).

*CRP crops are Conservation Reserve Program crops, which include vegetation beneficial for wildlife (FSA, 2011).

Indirect land-use change emissions of biofuels and Rob Lyons' 'Are corporations ruining food?'

Turns out that indirect land-use changes from agricultural expansion due to biofuels growth may actually sometimes be universally good! Or at least not as bad as a lot of research papers I've read suggest...

Yesterday, I attended the ‘Are corporations ruining food?’ talk by Rob Lyons, author of Panic on a Plate: How Societies Developed an Eating Disorder (2011) and a blog; he very briefly expressed a very interesting viewpoint on the problem of land-use changes due to increasing food production, suggesting that these changes may actually have a positive effect. Since biofuel production has a similar mechanism to food crop production, I will explain his argument further using some other research on the topic.

He highlighted the fact that most land-use changes to meet the increasing food production occur in the developing countries, meaning that substituting crop production for biofuels in the developed countries should result in higher imports from the developing countries. Lyons sees this as a positive social consequence for the poorer countries, (which are arguably in greater need of socio-economic improvements than the developed countries) as at the moment developing countries have difficulties in doing this due to restrictions imposed by unions such as the EU in the act to protect its their members' welfare.

Additionally, he suggested that the environmental impacts of imports is lessened or even mitigated when taking into account the energy needs of growing crops in countries such as Britain, where the cool climate results in major light, heating and cold storage requirements. The growing of biofuels is likely to require significantly less energy if varieties are chosen to enable their growth without greenhouses.

There are some large-scale projects in the UK designed to produce food in this way, for example, Thanet Earth in Kent (Derbyshire, 2008). The argument goes that growing these crops in warmer countries such as Spain will be less energy-intensive, producing less GHG emissions during growth, local transportation and cold storage, often compensating for the transportation emissions (Edwards-Jones, 2010). These GHG emissions from indirect land-use changes will be made even smaller if they occur on lands storing relatively little carbon at present, such as degraded lands. The importance of these cultivation emissions of local produce can be especially seen when considering that it accounts for ~83% of emissions in countries such as the US, instead of 11% for transportation, including long-distance (Weber and Matthews, 2008).

This is thus a potentially important point, which should be taken into consideration when calculating biofuel land-use change emissions, but does not seem to be included in reports at the moment.

However, while these benefits of long-distance land-use changes as a result of biofuel cultivation may exist fo some crops, looking at the bigger picture here, this is only relevant in some circumstances e.g. apples imported from New Zealnd are only GHG-saving for short periods of time twice a year, while the other abundant local produce such as broccoli is best-grown in the UK still (Edwards-Jones, 2010). Additionally, no land-use changes can be beficial in the abundant cases of rainforest destruction, the impacts of which will be discussed later in the blog.  In conclusion, I agree with my fellow UCL blogger, Megan Smith (please read Megan's view on the talk from a purely food production perspective), that it is worrying that Lyons is diminishing the importance of environmental impacts of agricultural activities.

Indirect emissions from biofuels: land-use change: introduction

Zamboni et al. (2011) and Gnansounou et al. (2011) articles, which will be the focus of this post, briefly raise some important issues regarding land-use change emissions of biofuels.

Biofuel cultivation often entails indirect GHG emissions through causing an increase in the global total cultivated lands e.g. forest to biofuel crop conversion; even in cases where biofuels are grown on previously-cultivated lands, it may still mean that uncultivated carbon-storing lands will have to be converted to agricultural in other parts of the world, which may produce substantial net GHG emissions (Zamboni et al., 2011). This is important as land-use changes arising from activities such as deforestation account for ~20% of global GHG emissions (Lange, 2011).

However, not all land-use change results in net GHG emissions from biofuel cultivation, due to spatial and temporal variations:

1. Biofuel cultivation may occur through cultivation of set-aside lands, which may make the emissions from land-use change insignificant (Zamboni et al., 2011).
2. Biofuel production may create useful by-products which further increase their efficiency and thus effectively decrease emissions per unit production e.g. DDGS for heat and power generation, or food for cattle  (Zamboni et al., 2011)
3. Land-use change taking place on degraded lands, which store little carbon, will likely have beneficial GHG saving effects (Gnansounou et al., 2009).
4. Emissions thus also depend on how much land is used for biofuel growth e.g. in EU substitution of ~10% of transport fuel with domestically-grown biofuels should not result in extra conversion of agricultural lands, while substituting any more than this will mean that food crops would have to be imported, increasing transport emissions, land-use change effect and thus biofuel emissions (JRC, 2008); this limits GHG saving potential of biofuels.

All these factors result in biofuel GHG emissions variations from land-use change of up to 6.4 times; the GHG emissions compared to gasoline may vary from -112% to +120% for the same production process (Gnansounou et al., 2009).

There are other problems with suggesting that emissions from land-use change should be included in biofuel emissions alculation; for example, the issues may prove to be highly controversial (Zamboni et al., 2011).

What factors determine the GHG savings of biofuels: cultivation emissions, part 2

• Sources of emissions variation in biofuel cultivation:

Synthetic nitrogen fertlizer: temporal and spatial cultivation management variations occur depending on where and how mineral fertilizer is applied, with the mineral nitrogen fertlizer synthesis being responsible for ~5% of the global natural gas consumption (Butterworth, 2009). GHG emissions from biofuels due to fertlizer application can result in 14% higher emissions than using fossil fuels (Zamboni et al., 2011). Firstly, nitrous oxide emissions from soils vary sptially and temporally due to temperature, precipitation, pH and soil organic carbon (SOC) (Ogle et al., n/d). Secondly, emissions depend on the efficiency of fertilizer application (Butterworth, 2009). Additionally, emissions come from fertilizer manufacturing, which usually uses fossil fuels, and from the direct nitrous oxide emissions from the soil (Crutzen et al., 2008; Zamboni et al., 2011). Although nitrous oxide emissions are smaller by volume than carbon dioxide emissions, the former is 300 times more potent (Zamboni et al., 2011).

However, since nitrous oxide emissions increse with inefficient appliction, they can be minimized e.g. in his book ‘How bad are bananas: carbon footprint of everything’ (2010), Mike Berners-Lee shows that avoiding the common practice of excessive fertilizer application can decrease GHG emissions from rice cultivation by a third. This also applies to biofuel crops, where if fertilizer is only added according to demand, emissions can be significantly reduced (Butterworth, 2009). Other ways in which these emissions can be reduced are suggested by Butterworth (2009). He proposes using household organic waste material compost as fertlizer, estimating that 600 US households produce enough waste to fertlize 10 ha of cultivated land, which would result in 1 te of oil in just a 'single coldpress'. Although some emissions will still occur, these emissions would have occurred anyway as the waste would have decomposed in landfill. This means no extra emissions will result from compost fertlizer for biofuel cultivation in this way. Additionally, compost decomposes and releases nitrates slower making them available for crop consumption more slowly than synthetic fertlizer, meaning there will be less 'leakage' of nitrates, as the supply is more likely to meet demand (Butterworth, 2009). Other research is being done into using gypsum waste from construction sites as fertlizer, which may also reduce emissions (UNCC, 2010).


Zamboni et al. (2011) also found that there are other economically and environmentally undesirable effects of excessive fertilizer application which decrease GHG reduction efficiency of biofuels. While fertilizers increase crop yield, they increase the protein and thus decrease the starch content in crops like corn, thus reducing the efficiency of ethanol generation (which requires starch) and of GHG savings (Zamboni et al., 2011). However, not using fertilizer at all is unrealistic, due to the lack of economic sustainability. If the protein-rich by-product, DDGS (dry distillers grains with solubles), is utilized for energy generation on the other hand, the process becomes much more efficient in terms of emissions saving and economic sustainability, resulting in a 54-63% GHG saving for wheat and up to 80% for corn Zamboni et al., 2011).

I know it's a lot to read, but you wouldn't want your bread to be grown on fossil fuels, would you? So we need to evaluate whether biofuels can be our saviour. To do this, keep on reading!

Machinery use: the other emissions from cultivation come from machinery use, which usually operates on fossil fuels and thus depend on the intensity of this use and on the fuel type used in the machinery. For example, Butterworth (2009) provides an example of how these emissions have been minimised on Bate's farm in Lincolnshire by running machinery on 100% biofuel produced sustainably on the farm, where the biofuel is grown using organic waste from the farm. However, please note that so far i have only managed to find one published example of a farm where the sustainable practices suggested by scholars like Butterworth are extensively employed to date, meaning that in practice machinery use and fertilizer emissions still remain relatively important (DFT, 2010).

Crop type used: this also affects GHG emissions and savings of biofuels, with crops that are not nitrogen-intensive, such as switchgrass, elephant grass and palm oil resulting in larger GHG savings, while nitrogen-intensive crops, like rapeseed may even result in a 1-1.5 times higher warming impact than fossil fuels (Crutzen et al., 2008). * This may be worrying as at present over 80% of biodiesel contains rapeseed (Crutzen et al., 2008). This reflects on the greater GHG saving efficiency of 2nd generation biofuels compared to 1st generation e.g. wsitchgrass and poplar result in 3 times greater GHG rediction than soybean-corn rotation (Adler et al., 2007).

Cultivation techniques: other aspects of cultivation management variations include the tilling method used ('tillage' is the preparation of soil for crop planting, through activities such as ploughing: PSU, 1996) e.g. the use of plough tillage reduces the soil organic carbon (SOC) content by 30% in 100 years for grassland soils, while if tillage is not practiced and winter cover crops are used, the SOC increases by 35%, thus indicating a major change towards net carbon uptake (Kim et al,, 2008). The SOC content of soils also differs, producing different emissions savings e.g. a forest soil has a higher SOC than a grassland soil and will therefore result in larger emissions and smaller GHG savings (Kim et al,, 2008). This land-use change effect will be discussed further in later posts.

Summary of the last two posts: assuming no major land-use change emissions from biofuels, cultivation may account for ~45% of total GHG emissions from biofuel production (Zamboni et al., 2011). Cultivation emissions arise mainly from synthetic nitrogen fertilizer application, machinery use and management practices such as ploughing; what is done with the by-products such as DDGS may also be crucial. Most of these emissions can theoretically be minimised significantly using appropriate management techniques, such as the monitoring of fertilizer application to make sure supply meets crop demand. However, this does not mean that such management has been extensively implemented in practice to date.

*Note: this figure may be considered an over-estimate, as the study included the emissions from manure. However, manure is a side-product of cattle-farming and the emissions are therefore only indirectly related to biofuels (Ogle et al., n/d). The debate into whether indirect emissions from biofuels should be incorporated into emissions calculations will be mentioned in later posts.

What factors determine the GHG savings of biofuels: cultivation emissions, part 1

The next two posts will constitute a limited literature review concerning cultivation emissions, a factor that may play an important role in determining biofuel GHG emissions savings relative to fossil fuels.

• Importance of cultivation emissions in total GHG emissions from biofuels:

This is the primary factor which results in the 7-77 % GHG emissions savings variation for wheat-derived ethanol, for example (DEFRA, 2007). However, the deemed importance of this factor varies between studies. For example, on the contrary to Schmidt et al. (2011), who concluded that agricultural emissions of biofuels are minor compared to the biofuel conversion process, Zamboni et al. (2011) suggest that cultivation conditions and management is responsible for ~45% of GHG emissions from biofuels. What is going on here – did one of the studies estimate this wrongly?

This is where an insight into the methodology employed, which I discussed in previous posts, is important to understand this. Zamboni et al. calculate biofuel emissions assuming previous agricultural land-use emissions were zero (i.e. land was not used for agriculture), while Schmidt et al. assume that land was previously used for agricultural purposes and thus only calculate the difference between biofuel production and other agricultural production. This means that both calculations are correct, depending on what the previous land-use was. In this post, the issue of land-use change will be put aside, meaning that Zamboni et al.’s findings are more relevant here.

• How do cultivation conditions vary:

They vary due to spatial and temporal climate, soil properties and cultivation management differences (Kim et al,, 2008). DFT (2010) suggested the importance of different cultivation factors towards the total emissions arising from cultivation. It found that nitrous oxide emissions from soil potentially accounts for 14-37% of total biofuel cultivation emissions; fertlizer synthesis may contribute 10-25% total emissions; the use of machinery may account for 13-34%; 7-34% of emissions arise during and after crop harvesting. These figures exhibit a lot of variation arising from the issues to be discussed below.

How many GHG emissions is biofuel expected to save: examples of estimates

These are some of the possible GHG savings expected from biofuels and the associated uncertainty, cited in the IEF report (2011).

       First generation biofuels:

      Second generation biofuels:

How many GHG emissions is biofuel expected to save: demand uncertainty

The speaker in this video, Jeremy Bentham (of Shell, not of UCL, fortunately, otherwise it would be most creepy), raises some other issues with calculating the potential GHG emissions savings of biofuels over time related to uncertainty, namely the future population growth.

7 days ago, the global population reached 7 billion people (Guardian, 2011) and if human numbers and the global economic development continue increasing at the expected rate, energy demands will be enormous in the future. This exact energy demand extent and the management strategies chosen in the future, such as how much of the energy demand will be accounted for by biofuels and how and where the biofuels will be produced, are a source of major uncertainty. As will be shown later in the blog, depending on the scenario adopted in the future, a great variety of GHG savings or emissions may result.

How many GHG emissions is biofuel expected to save: what reduces GHG emissions savings

This is a short video, which briefly introduces some of the factors that contribute towards the reduction of the potential GHG savings from biofuels. It exludes some issues, however, such as the direct emissions from nitrous oxide. It does also mention other environmental and socio-economic problems of biofuels, but please ignore these for now, as I will be discussing them later on in the blog!

What are the expected relative GHG emission savings of biofuels: uncertainty

The importance of calculating uncertainty in the case of biofuels: I have ended my last post saying that knowing uncertainty levels is important in good policy making. However, I have realized that I feel that I have not really explained this point, so I would like to do so now with this quick example.

 Figure 2.

I have found this diagram today in a presentation by Stanford University on uncertainty in biofuel production (Curtright, 2011). It focuses on the Calculating Uncertainty in Biomass Emissions (CUBE) model (figure 2), which is designed to estimate the uncertainty of all the components of the diagram in figure 2. The boxes indicated in green are the four components with the highest GHG emissions, with the two green boxes in the centre of the diagram also representing the components with the highest uncertainty levels.

These highest uncertainty levels probably arise because these components vary depending on the regional and temporal differences between sites (what the land was used for previously, organic matter availability in the soil and soil respiration rate), on what crops are grown (whether they are highly nitrogen-dependent or not, for example) and on what management techniques each individual farmer adopts (how efficiently fertilizer is applied and how intensively fossil fuel is used in cultivation). This therefore suggests that these high uncertainty levels probably arise because their management is difficult to control, as it depends on so many factors.

Identifying and understanding this uncertainty can be important to policy makers, as it shows that even if the GHG emissions from biomass conversion are the same for all biomass where the procedure has been standardized, the emissions of the biomass derived from different farmers and different areas are likely to still be very different. These uncertainty levels thus illustrate the importance of calculating emissions from biofuel that is grown at different sites separately in this case and reflect on the dangers of generalizing. Ignoring this uncertainty could lead to crude overestimates or underestimates of GHG emissions from biofuel production, while taking the uncertainty into account can allow to minimize emissions. For example, if the uncertainty is accounted for and the emissions are calculated specifically for each case, only the sites where biofuel cultivation is beneficial can be allowed to operate for the purpose.

What are the expected relative GHG emission savings of biofuels: uncertainty

The major sources of these uncertainties are mentioned in the RFA & DECC (2009) report, but they are not explained in detail there. The most comprehensive paper I have found so far which explains the uncertainties of GHG-saving potential of biofuels is the Johnson et al. (2011) article. You can explore the article to find out the details of the uncertainty sources, but here I will just review the points I found to be the most important and most interesting.

• One source of variability between models lies within which factors the model incorporates e.g. the modeller has to choose whether to include indirect emissions, such as due to land-use change and whether to stop at 2^nd or 3^rd order emission effects. I found this point most interesting, as the solution to avoiding this issue appears so straight-forward –  it seems that all one needs to do is incorporate as many factors as is possible, as surely this will make the model more accurate. Yet, world-class researchers seem to find this a difficult task!

I personally think that the best illustration of this is the Crutzen et al. (2008) study, which calculated that previous reports underestimated the climate change contribution of GHG emissions from biofuels by excluding the nitrous oxide emissions effects during cultivation. This has severe implications for policy-making: for example, rapeseed, a relatively common biofuel material at present, now potentially apparently contributes 1-1.5 times more towards global warming than fossil fuels instead of having a lower global warming impact as previously calculated. However, it seems that Crutzen et al. (2008) have not learnt from their own discovery of the importance of cultivation emissions, as their study excludes the emissions from fossil fuels used in the growing of biofuels. So why does this lack of incorporation of these variables continue happening?

At the moment, the best answer I could find was deduced from the Johnson et al. (2011) article, which is that the reason lies within the time and resources needed to account for all the possible factors that may affect GHG emissions of biofuel production. Ekval and Weidema point out that trying to include all the possible emission sources can continue indefinitely (Johnson et al., 2011). Johnson et al. suggest only including the most likely and the most significant parameters to account for this problem. However, I hope I have illustrated that this is not always so straight-forward at the moment, as it is often difficult to predict which factors are important without exploring all of them in the first place. This suggests that since this is impractical to do and all the possible sources of emissions have probably not been incorporated into current models yet, the present estimates of biofuel impacts may still change in the future.

• Another major source of uncertainty is the variation in time and space. It is impossible to decide ‘correctly’ on what data would constitute typical emissions on a larger temporal and spatial scale, as this would be ignoring differences in agricultural practices, in energy input and yield output and in soil carbon storage, as well as numerous other factors (Johnson et al., 2011). It is also impossible to predict accurately the future development in technology, agricultural practices and social and economic development. This will thus affect the use of biofuel and the emissions estimates from biofuel production.

• Uncertainty in allocating GHG emissions also arises where a material has multiple products. For example, growing corn for biofuel produces both grain and stover, where one of these products can be utilized in biofuel synthesis and the other used for another purpose, such as food. It would be near to impossible to separate the emissions due to biofuel alone here.

• The other sources of uncertainty lye within, for example, a lack of sufficiently detailed data on certain processes.

• Scenario uncertainty also exists, such as the percentage of biofuel to be used in transport in the future, which is subject to economic and political factors that can not always be predicted, for example.

In conclusion, there is a number of reasons for the often high variability in the estimates of the relative biofuel GHG savings between and within reports. This variability means it is important to keep in mind that the topic of biofuels being discussed in this blog is based on rather uncertain data. However, as with other such issues where full scientific certainty is impossible at present, management decisions still have to be made despite this uncertainty, so it is important to make the most well-informed judgement on the benefits of different actions possible. In order to be able to do this, knowing the potential sources of uncertainty in the data, some of which are outlined in this post, is useful.

What are the expected relative GHG emission savings of biofuels: uncertainty

Blog summary so far: We have seen that while biofuels may have acted as a carbon sink historically, their properties seem to have changed since then due to the new factors that arose. It has also been shown that the calculations of GHG savings from biofuels contain large uncertainties and also vary significantly between the different materials. In my next post I will attempt to explain the uncertainties in the savings estimates.

Uncertainty - an introduction: A number of reports currently state that 1^st generation biofuels, which include mainly food crops high in starch and sugars, such as corn and sugar cane (Tao et al., 2011) are estimated to produce ~60% GHG saving compared to fossil fuels, while 2^nd generation biofuels, which include mainly cellulose-rich materials, such as corn stover, switchgrass and jatropha (Tao et al., 2011), are expected to produce ~80% carbon saving (figure 1).

 Figure 1.

However these figures are not an accurate representation of the reality, as they greatly mask the complexities underlying the issue of GHG emissions estimation of biofuels, which can be partially seen in the wide uncertainty level in the data from my previous post and from the wide uncertainty level bars in figure 1. Please also note that the figure does not incorporate the future 3^rd and 4^th generation biofuels which are likely to have even larger uncertainty levels at the moment.

To better understand the current and future carbon reduction potential of biofuels, in my next post I will explain some of the assumptions made in these calculations and the factors that produce the high uncertainty levels and the wide range of outcomes before presenting the GHG reduction potential data in greater detail.

How much Carbon and GHG emissions is biofuel expected to save?

I would like to start with perhaps the most optimistic view of the potential carbon saving impact of biofuels to achieve juxtaposition of the theory underlying the concept of biofuels with the reality of their effects in practice.

In his work, Bill Butterworth uses the Carboniferous Era as a model for biofuels. He suggests that approximately 350mya, the death of the vegetation that later formed our contemporary fossil fuels acted as a carbon sink, where the amount of GHGs that was taken up by the plants during their life exceeded the amount that was released. The idea of biofuels thus also parallels with that of farming, Butterworth points out, where the crops uptake carbon dioxide and release oxygen during growth. While GHGs are emitted on death, this happens at such a slow rate that it makes the process sustainable, enabling farming practices to take place for over 10,000 years (Butterworth, 2009 and Butterworth, 2009).

‘So why on Earth has the issue of climate warming not been resolved yet?’, was the question that left me unconvinced after I first read his book.

One only has to look a little closer to realize that the answer lies within using the processes of the Carboniferous 350mya and farming practices 10kya as analogues for the present. The first limitation to this approach is that machinery and synthetic fertilizers were not used to promote vegetation growth during those times. These usually operate on fossil fuels, decreasing the carbon saving efficiency of biofuels in practice. Additionally, in reality there are other factors that are not taken into account by Butterworth’s model. These are reflected in the following estimates of GHG reduction potential calculated by the Renewable Fuels Agency and the Department for Energy and Climate Change (RFA & DEC, 2009).

For example, synthesising ethanol from European sugar beat in the UK was calculated to result in either ~30% carbon saving or ~30% carbon increase in comparison with fossil diesel. Similarly, using tallow as biofuel in the UK may produce 56% less carbon in the best-case scenario, but may amount to releasing 13% more carbon than fossil fuel diesel in the worst-case scenario. 

On the other hand, the calculations are highly optimistic for other types of material. For example, the greatest carbon saving results from MSW (municipal solid waste), which produces a ‘carbon saving’ of 193% compared to fossil fuel (RFA & DECC, 2009). Utilizing wheat straw in the UK was also calculated to result in a high carbon saving of 80% compared to fossil diesel (RFA & DECC, 2009).

The question that this raises is why are there such large uncertainty levels for some biofuel materials and not for others, and why some biofuel materials result in significantly higher carbon savings than others, and what does this show about how ‘green’ biofuels are overall.

Putting biofuels into the wider context: my current opinion on the matter

Prior to launching into the discussion on the effectiveness of biofuels in dealing with the problems they could potentially resolve (or create), I would like to put biofuels into the wider context and express my current views on the actions humanity should take to attempt to resolve the problems of energy security and climate change.  

Primarily, I would like to stress that I believe that global action should be taken towards drastically reducing humanity’s emissions of GHGs. This means that renewable energy should not be used as an excuse to continue with the highly energy-consuming lifestyle of the developed world. This opinion is based on the rate at which this supposedly serious problem is being addressed, as the results of the Copenhagen meeting, which did not amount to much action (Guardian, 2009), show. Additionally, the schemes which have actually been put to practice are often not effective enough at all: in 2001, only 15% of consumers knew that the EU Flower was an eco-label, with very few knowing what manufacturing practices it actually reflected (Pedersen and Neergaard, 2006). How can this lead to ‘greener’ consumption, when there is such a lack of communication between the different domains of governance, which in this case is between the markets and the consumer?

I think that the rate of change is so low mainly because everyone shifts the responsibility of dealing with climate change onto someone else, creating a vicious circle of inaction. Here, the citizens of developed countries shift the responsibility onto the governments, the governments of the developed countries – onto governments of the developing countries, onto technological advances or onto the market, and the market – onto consumers and governments. Ideally, I believe that all three domains of governance should be employed in dealing with the issue, where governments, people and industry should all be involved in reducing emissions.

The slow rate of action to mitigate climate change also reflects the unwillingness of the developed countries to change their lifestyle: for example, the target of 80% carbon emissions reduction by 2050 has been dropped; instead, the U.S. has only agreed to reduce their emissions by 4% of the 1990 levels as a result of the recent Copenhagen meeting (Guardian, 2009). Since it is these countries that are the biggest emitters of GHGs, it seems that it would be highly unrealistic to suggest that it would be possible to reduce the global energy requirements by changing lifestyle in the short-term.

However, reducing the global energy consumption would be important in the long-term, as it is possible that ‘green’ energy will not be able to meet all energy requirements if these remain at the current level of the developed countries. This especially holds true when considering the future threat posed by population growth and the continued development in the lower-income countries where most of this growth occurs.

Nonetheless, in the short-term, switching to renewable energy seems like a more practical near-future solution to me at the moment, as this does not assume lifestyle changes. Biofuel is one such source of renewable energy and therefore it is important to consider whether it should be employed.

What is 'biofuel':

‘Biofuel’ is a renewable energy source derived from contemporary biologically-based materials, which can be utilized in the place of petroleum fossil fuels (Demirbas, 2009).

Why use biofuels: lessons from history and other reasons:

Biofuels have been used since humanity’s discovery of fire when wood was burnt for heating and cooking. Biofuels were then also employed when electricity was first discovered, before the properties of fossil fuels were fully explored; similarly, the first diesel engine, designed in the 19th century, was run on peanut oil. Fossil fuels did not gain in popularity until after 1926, when crude oil resources began to be more heavily explored, making them a significantly more efficient and cheaper transport energy source than biofuels (Pousa et al., 2007; Biofuel; 2010).

The demand for biofuels had increased in Europe during World War II due to the temporary fuel shortages which arose, but then fell again afterwards, owing to cheap oil influx from the Middle East and the Gulf countries. Nonetheless, the issue of energy insecurity was brought up again in the 1970s, when OPEC (Organization of the Petroleum Exporting Countries) made major reductions in oil exports to non-OPEC member countries after a geopolitical conflict. A similar crisis occurred in the 1990s. These experiences, as well as the increased environmental awareness and the realization of the finite nature of fossil fuel resources, contributed to the renewed increase in biofuel interest in the recent decades (Pousa et al., 2007; Biofuel, 2010).

Stakeholders, such as the European Commission (EC) (DFT, 2010) and the U.S. Renewable Fuel Standard (RFS) (Worldwatch Institute, 2009), now stress the importance of reducing humanity’s dependence upon fossil fuels and switching, at least partially, to renewable energy sources in order to 1) reduce global greenhouse gas (GHG) emissions to help mitigate future global warming and 2) decrease dependence on the shrinking fossil fuel resources to ensure greater energy security (EC, 2006 and DFT, 2010). Biofuels are one source of renewable energy.

However, there has been a substantial amount of controversy surrounding biofuels (e.g. Guardian, 2011; Independent; 2011). This made me very intrigued to reason for myself whether biofuels are the way ahead, relating to helping mitigate the aforementioned issues of reducing the global GHG emissions and fossil fuel dependence, or the blind alley, creating more problems than they resolve.

References:

Biofuel (2010) Biofuels the Fuel of the Future: History of Biofuels, (http://biofuel.org.uk/history-of-biofuels.html; 12 October, 2011).

Demirbas, A. (2009) ‘Political, economic and environmental impacts of biofuels: a review’, Applied Energy, 86, 1, 1 – 10.

Department for Transport (DFT) (2010) Regional Emissions from Biofuel Cultivation Revised Report (http://assets.dft.gov.uk/publications/regional-emissions-from-biofuels-cultivation/cultivations.pdf; 11 October, 2011).

European Commission (EC) (2006) Biofuels in the European Union: a Vision for the 2030 and Beyond (http://ec.europa.eu/research/energy/pdf/draft_vision_report_en.pdf; 11 October, 2011).

        Guardian (2011) Environment: Biofuels (http://www.guardian.co.uk/search?q=biofuels&section=environment; 11 October, 2011).

        Independent (2011) Biofuels (http://www.independent.co.uk/search/index.jsp?eceExpr=biofuels; 11 October 2011).

Pousa, G. P. A. G., A.L.F. Santos and P.A.Z. Suarez (2007) ‘History and policy of biodiesel in Brazil’, Energy Policy, 35, 11, 5393 – 5398.

Worldwatch Institute (2009), Worldwatch Issue Brief – U.S. Biofuels: Climate Change and Policies, Washington DC (http://www.worldwatch.org/files/pdf/Biofuels%20Issue%20Brief.pdf; 11 October, 2011).