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!