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).