Biofuels : a viable alternative ?

Carte blanche published in the belgian newspaper "Le Soir" on july 30th 2007.
by Hubert Halleux, Assistant at the University of Liège’s Industrial Chemistry.


European directives anticipate an integration of a minimum of 5.75% biofuels into the transport sector by 2010, and 10% by 2020. ‘Organic’ fuels are attractive, but have a mixed environmental balance sheet. Moreover, using agricultural land for their production will have significant consequences.

The development of products which have the best possible environmental performance is at the heart of our concerns. In the transport sector, biofuels appear to offer a partial solution to the consumption of fossil fuels and global warming.

If the first advantage is easily understood to lie in the ‘renewable’ nature of these fuels, the second advantage merits further explanation. In effect, the carbon dioxide (C0²) emitted when they are burnt forms a part of carbon's natural cycle. The quantity of CO² emitted is equivalent to the quantity the plants had previously absorbed during their growing cycle. A priori, then, the use of biofuels does not lead to increases in the quantity of greenhouse gases in the atmosphere.

Nevertheless, to evaluate a product’s environmental performance it is necessary to consider the whole of its life cycle, from the purchase of products used in its production, to its utilisation and destruction. Moreover, other environmental impacts must be taken into account, such has damage to human health or acidic gas emissions. The life cycle assessment (LCA) methodology, also called ‘ecobalance assessment’, allows for such a complete and overall approach.

There exist two forms of biofuel: an ‘oil-producing’ kind and an ‘ethanol’ type of fuel. The first consists of producing a vegetable oil (rapeseed, palm) which can be transformed into a biodiesel whilst the second consists of producing ethanol from sucrose (beetroot, sugar cane) or starchy (cereals, potatoes) plants through the process of fermentation. The crops which allow for the largest production of biofuels per hectare for each of these two forms in Belgium are rapeseed and beetroot.

In order to establish an environmental balance sheet for each of these two fuels, each stage of their production needs to be studied. The first stage is growing the plants. This demands the production and application of fertilisers and pesticides, the use of agricultural machines, etc. The second stage is the production of the fuel itself from the biomass. Rapeseed oil must be extracted from seeds and then transformed into biodiesel by chemical reaction. This production generates two by-products: rapeseed cake (the residue left after the oil has been crushed out of the seeds), rich in protein and thus a useful food for livestock, and glycerine, which finds a market in the chemical industry.

To produce ethanol, a sugary juice is extracted from beetroot and is then fermented. The residue pulp of beetroot constitutes a by-product with much less value-added than that of rapeseed: it requires a drying out process that is particularly energy greedy and its sugar and protein content is low.

Considering these stages together, the overall energy balance sheet is less favourable than predicted. In effect, the energy saved in the use of biofuels is only 48% in the case of biodiesel and 41% for bioethanol (this means that we would consume 48% or 41% less fossil fuel energy if we worked only with biofuels).

It should be pointed out that the biodiesel balance sheet could be improved if its by-products were made full use of. In effect, in avoiding the production of the products they are substituted for, one avoids significant energy consumption. The benefit of the 'biodiesel' type of fuel then comes to a figure of 74%. As was mentioned above, beetroot by-products do not offer such a benefit.

The emission of greenhouse gases being directly linked to the consumption of fossil fuels, a reduction of these emissions follows a similar trend in energy saving rates.

Once a complete ‘ecobalance assessment’ of the biofuels has been carried out, it is realised that the use of land is the most critical parameter. In effect the monopolisation of land for their production entails a reduction in the possibilities of growing foodstuffs, thus leading to a rise in the cost of the latter. According to a recent report by the OECD which analysed the situation, the price of cereals will rise further by between 20 and 50% between 2006 and 2016.

To feed the whole of the Belgian car park completely with biofuels it would be necessary to cultivate an area of land with a larger surface area than the country itself: one hectare allows for the production of around 1.5 tons of biodiesel (rapeseed) or 4 tons of bioethanol (beetroot). A comparison of these yields would suggest that growing beetroot would be more advantageous. However, growing a hectare of rapeseed also produces two tons of food material for livestock, allowing for the saving of a large area which would have to be used to produce an equivalent amount of food of the same nutritional value. Taking this parameter into account, it is concluded that the production of biodiesel is less critical than that of bioethanol in terms of land use.

When one takes into account the total of all the environmental aspects, one realises that their benefits are demonstrably weaker than had been anticipated. Moreover, whilst better yields per hectare can be obtained in other climates (sugar cane or palm oil), in terms of land availability the contribution of biofuels to the energy market will remain marginal, unless it enters strongly into competition with the food sector. In this case, we can expect an acceleration in the rise of foodstuff prices, which is already a sensitive issue the world over. This last aspect will have a particularly large impact on the world’s poorest populations, in the North as well as in the South. Does the slight environmental benefit justify such investment and disruptions?