From promises to doubts

In Europe, it is transport that is responsible for the biggest increase in greenhouse gas (GHG) emissions. This is a trend that the new European directive would like to reverse by having biofuels meet 10% of transport sector needs by 2020, as opposed to 2% at present. However, the use of biofuels is also raising many fears about the possible environmental and social impact. It is no doubt optimistic to believe that these concerns will be allayed by the second generation of biofuels.

© Shutterstock
© Shutterstock
Mise en place d’un micro réacteur en verre à lit fixe pour l’évaluation de catalyseurs en vue de nouveaux procédés de production propres. © CNRS Photothèque/Emmanuel Perrin
Installing a glass fixed bed micro-reactor to evaluate catalysts with a view to developing new clean production methods. © CNRS Photothèque/Emmanuel Perrin
Étude de réaction catalytique pour les carburants verts. Ce dispositif permet d’étudier les performances (activité, sélectivité, durée de vie) d’un catalyseur solide. © CNRS Photothèque/Emmanuel Perrin
Study of the catalytic reaction for green fuels. This device makes it possible to study the performances (activity, selectivity, life) of a solid catalyst. © CNRS Photothèque/Emmanuel Perrin

It is the Royal Society (UK) that sounded the warning, in its January report entitled Sustainable biofuels: prospects and challenges. “Unless biofuel development is supported by appropriate policies and economic instruments that address these issues, then there is a risk that we may become locked into inefficient – and potentially environmentally harmful – biofuels supply chains.” The House of Commons Environmental Audit Committee went even further in calling for a moratorium on biofuels. At the very time when the European Union is aiming for a 10% share of biofuels in the transport sector by 2020, many politicians, scientists and members of civil society are stressing the uncertain carbon footprint of biofuels, their environmental consequences and the higher food prices they are generating.

Emissions: no consensus

The GHG emission savings generated by biofuels depend very much on the parameters taken into account. Renton Righelato, President of the World Land Trust, and Dominick Spracklen of Leeds University (UK)(1) consider that the model used by the European Commission fails to take into account the indirect effects of converting land and forest for Prize winner for chemistry, estimates that the amount of nitrogen in fertilizers that is converted into nitrous oxide (N20) – a greenhouse gas almost 300 times more powerful than CO2 – is between 3% and 5% rather than the current estimate of 2%. Another example: the ADEME estimates the increased greenhouse gases resulting from ethanol produced from wheat to be 60 %, while the scientists and industrialists at the Commission’s Joint Research Center (JRC) put this at somewhere between – -8 % and + 80%. It is all a question of how one evaluates the share of refining co-products in the gains or the sources and quantities of energy needed for production.

Eat or drive?

In the EU today, 81 % of land is given over to forests or crops and available fallow land represents no more than around 11 % of cultivable land. However, achieving the 10% biofuel target would require the use of between 15% and 38 % of the land, depending on the studies. There is thus a real risk that the growth of biofuels will result in significant damage to the environment, with the loss of ecosystems, intensive farming, soil degradation, deforestation and increased water consumption. “As long as markets do not correctly take the environment into account, there will be a major incentive to convert natural ecosystems into plantations for biofuels,” writes the OECD in its 2007 report entitled Biofuels: is the cure worse than the disease?

The OECD also estimates that subsidies granted to biofuels have the effect of diverting land from food crops, thereby causing prices to rise. With a 40% increase in food prices in 2007, a 52 % increase in wheat prices and a 70 % increase in oilseed and vegetable oil prices (Food and Agriculture Organization – FAO – figures), the choice between fuel and food is becoming very pertinent. This is not as serious in the rich countries – where food prices rose by “just” 22% between 2000 and 2007 – as in the least developed countries where the price rise is a staggering 90 %. Although biofuel production is not the sole cause of the rise, the FAO nevertheless cited it as one of the four causes identified.

A necessary new generation

The Commission is not insensitive to these criticisms and is seeking to reassure by guaranteeing that land considered to be ”carbon sinks” or with a high degree of biodiversity will not be converted. It is also counting on the second generation of biofuels – although they are not expected until 2015 – to improve the poor ecological and human balance of the first generation. Although using wheat and maize to produce bioethanol or growing colza for biofuel is fuelling concerns, the use of plants not dedicated to food production is likely to allay them. There will be no more oilor sugar-based plants needed as the second generation aims to transform lignocellulose directly into alcohol or hydrocarbons.

Consisting of 25 % lignin, 50 % cellulose and 25 % hemicellulose, lignocellulose constitutes the greater part of the plant biomass found in wood, leaves, tree and shrub stems and all herbaceous species.

Biological conversion

It is possible to convert this plant matter into fuel biologically. As cellulose is a polymer formed of glucose chains, the biological method involves recovering these sugars and converting them into ethanol through a process of fermentation. Although man has been able to produce alcohol from sugar for thousands of years, separating the cellulose from plant fibre (representing between 9% and 17 % of the cost of cellulosic ethanol) and then breaking it down to extract the glucose (between 20% and 33 % of the cost) is not so easy. The European project – New Improvements for Lignocellulosic Ethanol (NILE) – aims, among other things, to find a good panel of enzymes with which to recover the glucose through enzymatic hydrolysis. Their team is interested in cellulases, enzymes present in mushrooms (Trichoderma reesei), bacteria or other organisms that feed on raw plant matter, with a view to selecting the best candidates, combining them and developing production frameworks for boosting yields.

Biological conversion is far from optimal and only uses cellulosic sugars, disregarding hemicellulosic pentoses, sugars for which we have not yet mastered the fermentation processes. The NILEproject is seeking to increase the yield and speed of enzymatic hydrolysis and increase the amount of ethanol produced per unit of dry matter, which is currently between 12% and 16%. Project coordinator Frédéric Monot believes that “current research should improve the yield of enzymatic hydrolysis, open up new avenues for exploiting pentoses and make better use of lignin.”

Thermal conversion

The other solution is to heat the plant matter under conditions of high pressure and low oxygen, thereby “breaking” the molecules to extract a gas that is a mixture of carbon monoxide and hydrogen. This gas is then transformed by catalysis using iron or cobalt to obtain a hydrocarbon wax that is then refined into synthetic fuel. Although improvements are necessary to pretreat the plant matter, limit the formation of impurities during gasification and then filter the gas, each element in the chain is operational today. The next step is to bring them all together within a production unit that is sufficiently profitable. The chain of collecting, transporting and storing the raw materials represents a considerable cost, with the difficulty lying in finding the critical industrial size that makes it possible to maximise production and minimise the distances travelled to collect the biomass.

With a yield currently estimated at 15% fuel per dry matter unit, the German Energy Agency estimates the production potential at 4 000 litres per hectare. This would enable Germany to meet 20% of its total fuel consumption. The European biofuel platform tempers this enthusiasm, however, stressing the need for vast investment to industrialise the process – investments that the technological and commercial risks do not encourage.

Not all is resolved

Today, Etienne Poitrat considers the biological route to be the most advanced, while stressing that “the demand for diesel being strong and with the biological process unable to meet this demand, there is certainly a role for thermal conversion.” Yet these new techniques do not really ease the concerns raised by the first generation. Waste recovery is unlikely to meet more than 15–20% of biofuel needs and, despite a 35 % forest cover in Europe, the quantity of remaining exploitable forest remains marginal. As to straw and other agricultural residue, their use for energy purposes is in direct competition with other sectors that use them, such as stock farming, crop farming and the paper industry.

It is therefore impossible not to have land dedicated specifically to growing ligneous plants for biofuels.

Although high lignocellulose levels and a chemical structure that facilitates the extraction of sugars by biological means are essential criteria for these “energy plants”, they must also be perennial, require little water input, be fast growing and cultivable on land unsuitable for growing food. The varieties in view are herbaceous plants such as miscanthus or switchgrass and trees such as the poplar, the willow or the locust tree. EPOBIO, a joint European and US research group, is studying these species to describe their varieties and identify their most interesting characteristics.

Once the genetic sequences have been identified, the EPOBIO researchers will have to select, hybridise or genetically modify the different varieties to arrive at strains that are most suited to biofuel needs.

Moreover, even optimised to provide yield per hectare that is superior to that of the colza used for first generation biodiesel, these plants do not completely resolve the issue of the GHG balances for which it is becoming essential for the various stakeholders to agree on a calculation method accepted by all. European Environment Commissioner Stavros Dimas stresses that “the responses to social and environmental issues are precise and incorporated in the text”. Of the arguments that fail to convince environmentalists, Friends of the Earth describe these responses as “particularly unsubstantial, offering no guarantee of sustainability.”

Question of confidence

Is the EU awarding too much importance to these biofuels? Perhaps. But how to respond to the urgency of the need to reduce greenhouse gas emissions and the depletion of oil resources? Although Europeans may be sceptical about biofuels, that does not mean they are ready to leave their cars in the garage. It is development. As many experts state, biofuels not cause other avenues to remain unexplored.

François Rebufat

  1. Carbon Mitigation by Biofuels or by Saving and Restoring Forests? Science Vol 317, August 2007
  2. Energy and GhG balances of biofuels and conventional fuels - Convergences and divergences of main studies, ADEME, July 2006


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