Proponents of biofuels often call them ‘climate neutral’. But are they? And what are their requirements regarding natural resources?

Fuels derived from biological materials (‘biofuels’) have a significant role in energy supply. This increasingly also holds for advanced industrialized economies. Electric power plants in such countries increasingly burn ‘biomass’. Municipal waste incinerators and incinerators of sewage sludge supply ‘green electricity’ by burning organic wastes. There is an increasing production of ‘biogas’. And bioethanol and biodiesel are by now common admixtures to transport fuels.

In recent years, a lively discussion has emerged about biofuels. This has mainly been sparked by liquid biofuels, such as bioethanol, biodiesel and palm oil. Both in the United States of America and the European Union, the emergence of liquid transport biofuels was largely a product of agricultural policy. Growing crops for liquid biofuels was intended to improve farmers’ incomes. When this policy did prove very successful in 2008, because the increase of transport biofuel production appeared to contribute significantly to higher food prices, mainstream public opinion became largely critical about transport biofuels. Another cause for criticism was the expansion of palm oil consumption for the production of electricity and biodiesel. This expansion appeared to be linked to cutting down tropical forests, negatively affecting biodiversity and the survival of one of our closest relatives: the orang utan.

A factor that is important for the impact of expanding biofuel production on food prices and living nature, is the relatively large land requirement of biofuel production. The worldwide most efficient biofuel crop is sugarcane. However the energy embodied in bioethanol made from sugarcane is only about 0.16% of solar irradiation into sugarcane fields. A hectare of solar panels is able to provide for about a hundred times more car-kilometers than a hectare of sugarcane.

Sugarcane Field

In the following the emphasis will rather be on two matters that have attracted less public interest than the impact of biofuels on food prices and nature: the impact of biofuel production on climate and biofuel requirements regarding natural resources.

Climate neutral?

Proponents of biofuels often call them ‘climate neutral’. The idea behind climate neutrality is this: if one burns biofuels, CO2 is released that was recently sequestered by plants. The net result thereof on the atmospheric concentration of CO2 is therefore: zero.
A substantial amount of research has been done about the life cycle greenhouse gas emissions of biofuels. This research shows that such emissions are substantially at variance with climate neutrality.
A fist reason for this is that processes used in the life cycle of biofuels may consume fossil fuels. This is at variance with climate neutrality. The input of fossil fuels in the biofuel life cycle may be quite high. In case of drying and burning sewage sludge the input of fossil fuels is in practice roughly the same as the energy yield. The input of fossil fuels in the production of bioethanol from corn or wheat in industrialized countries tends to be about 60-80% of the energy content of the bioethanol produced. All methods for producing algal biofuel that have so far been applied, require more energy than they yield.
A second reason for the deviation from climate neutrality is that the cultivation of biofuel crops leads to the release of substantial amounts of the potent greenhouse gas N2O.
Thirdly, the biofuel life cycle may lead to significant changes in biogenic carbon stocks, both aboveground and in soils. For instance a hectare of European arable land used for the production of biofuel crops on average loses about 800 kg of carbon per year. This adds to the atmospheric concentration of CO2. Also, when a tropical forest is replaced by oil palms or sugarcane the aboveground carbon content of the latter is much lower than the former. The difference between the two again adds to the atmospheric CO2 concentration. Furthermore, when cultivation for biofuels increases, demand for food is inelastic in relatively rich countries. If in industrialized countries cultivation of biofuel crops expands, the consumption of bread or meat in such countries is not significantly reduced. Thus, when crop production for biofuels in Europe or the USA expands rapidly, food and feed has to be imported from elsewhere, in practice mainly from Latin America. And for the expansion of food and feed production in Latin America there is substantial clearance of tropical forest or savannah (Cerrado). Such clearance leads to a net reduction of biogenic carbon stocks and adds to the atmospheric concentration of CO2.

The net result is that biofuels are often not climate neutral. The life cycle greenhouse gas emissions linked to bioethanol from corn or wheat or biodiesel from rapeseed are even larger than the life cycle greenhouse gas emissions linked to conventional gasoline and diesel fuel. When currently available palm oil is burned for power production, life cycle greenhouse gas emissions are larger than in the case that fossil fuel oil is used for electricity generation. This does not mean that all biofuels are counterproductive. When for instance forest residues from sustainably managed forests are burnt, the greenhouse gas balance tends to be much better than in the case of burning fossil fuels.

Biodiesel

The criticisms regarding ‘first generation’ liquid biofuels like bioethanol from wheat or biodiesel from rapeseed have by now led to calls for ‘second generation’ biofuels. These should be made from lignocellulosic materials (plant fibres). In this context the cultivation of lignocellulosic crops such as willow, switchgrass and Miscanthus is often favored. These crops are inedible. So, the reasoning apparently often is, this cultivation will have no impact on food prices. This is unfortunately not correct. Under market conditions there is strong pressure to use good soils for the production of lignocellulosic biofuel crops because of a higher profit. This will lead to competition for such soils with food crops. Also there is competition for inputs such as fertilizer. Due to this competition, lignocellulosic biofuel crops will have a substantial upward effect on food prices when their cultivation expands rapidly.
But, are lignocellulosic crops good for limiting climate change? This would not seem very likely. As demand for food is inelastic, a rapid expansion of lignocellulosic biofuel production on good soils would lead to a significant clearance of nature, having a negative impact on biogenic carbon stocks. Also substantial inputs of fossil fuels and emissions of N2O linked to the lignocellulosic biofuel life cycle seem likely.
However, biofuels can substantially contribute to limiting climate change when their cultivation is restricted to abandoned soils that currently sequester little carbon. This, however, requires that one goes beyond the market, as prices for biofuels will be significantly higher than when good soils are used for crop cultivation.

Natural resources

The natural resource requirements of biofuels are substantial. A good illustration thereof is the price of phosphate fertilizer. This increased by a factor seven during the years 2007-2008, and the growing demand for phosphate linked to cultivation of biofuel crops substantially contributed to this price rise. The requirement of biofuel production for (arable) land is also large. Above, the modest biofuel yield from sugarcane cultivation was referred to. But other biofuel crops lead to even larger land claims. When for instance the complete corn harvest in the United States is converted into ethanol, and when the energetic value thereof is corrected for the input of fossil fuels, the ethanol yield energetically equals about 3% of US gasoline demand.
Moreover, it is of utmost importance that soils remain fertile. This strongly limits the use of organic residues, such as harvest residues, for biofuel production. As pointed out above, a hectare average arable land in the European Union loses about 800 kg of carbon yearly. Such a loss in the long term has a negative impact on soil fertility. Therefore it is important to the reduce carbon losses from arable land to zero. When one does not change tillage, the only feasible option is to return much larger amounts of organic residues to arable soils. In this case it is unlikely that substantial amounts of organic residues remain which can be used for biofuel production.
Another important requirement is the additional demand of water for biofuel production. In a substantial number of regions fresh water is already scarce. In China, where fresh water is scarce, for instance plans to expand biofuel production are subject to substantial criticism because of the large water demand involved. Current Chinese targets for biofuel production imply an additional water demand that roughly equals the discharge of the Yangtze river. Switching all transport to biofuels worldwide, would imply an additional yearly fresh water demand of at least 5000 km3, which is about 40% of all fresh water which mankind could reasonably consume.
Finally, there is the matter of minerals cycling. Above, it was pointed out that burning residues from sustainably managed forests has usually a much better greenhouse gas balance than fossil fuels. However, such residues are relatively rich in minerals (such as potassium, phosphate, calcium and magnesium). And when these minerals are not returned to the forests from which the residues originated, in the long term the growth of trees in such forests will be reduced. So far, such cycling of minerals is not much practiced.

The Yangtze River in China

Conclusion

The rapid expansion of biofuel production leads to many questions. These questions regard food prices, impacts on nature and climate and the demand for natural resources. So far these questions have not led to a serious re-evaluation of biofuel policies. The absence of a serious re-evaluation is linked to the major agrarian, commercial and geopolitical interests, which are at stake. In the absence of a serious political re-evaluation, increasing biofuel production will cause more hunger and significant environmental damage. In principle it is possible to generate a substantial amount of biofuels without a substantial impact on food prices and in a way that limits climate change. Low-input cultivation of biofuel crops on abandoned agrarian soils which currently sequester little carbon, and residues from sustainable forestry can be used for this purpose. But the political will to implement this option is so far absent.

Prof.dr. Lucas Reijnders.
Professor of Environmental Science at the Open University of the Netherlands.
Professor of Environmental Science at the University of Amsterdam

References:

• D. Cordell, J. Drangert & S. White. The story of phosphorus: global food security and food for thought. Global Environmental Change, ter perse (Publication, Presentation)
• L. Reijnders. Transport biofuels: can they help limiting climate change without an upward effect on food prices? Journal of Consumer Protection and Food Safety 2009; 4: 75-78 (Publication)
• L. Reijnders. Microalgal and terrestrial transport biofuels to displace fossil fuels. Energies 2009; 2: 48-56 (Full report)
• L. Reijnders & M.A.J. Huijbregts. Biofuels for road transport. A seed to wheel perspective. Springer, London 2009.(Book Amazon)
• N. Yang, Y. Zhou & J. Liu. Land and water requirements of biofuel and implications for food supply and the environment in China. Energy Policy, ter perse (Publication)