Course: BFM 101 Biofuels Fundamentals

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Biofuels: Some of the Issues

There are many issues to be considered and weighed up regarding the use of biofuels. The following points will help you to consider further the various implications of using trees, food crops and grasses as fuels.

How does the cost of biofuels compare with that of conventional fuels?

At present, the cost of producing biodiesel and bioethanol is approximately double that for conventional fossil fuels. The UK offers tax incentives to encourage fuel producers to make biofuel and there is also an incentive for consumers: the duty on petrol with 5% biofuel is, at the time of writing (2009), 20 p/litre less than that on ultra-low sulphur petrol.

A recent review has shown that biofuel production is a high-cost process overall; only the production of bioethanol from sugar cane was considered to be cost-effective. If, however, the price of crude oil rises then biofuels may start to become more competitive, although this would depend on fertiliser, and hence biofuel feedstock, prices remaining stable.

Does growing crops for fuel create higher food prices?

One point of view is that using land to grow crops for fuel rather than for food has led to increased food prices, which in turn impacts most on those in developing countries who have to spend a relatively large proportion of their income on food. In 2007, the United Nations Food and Agriculture Organisation (FAO) and the International Food Policy Research Institute (IFPRI) both released reports suggesting that rising food prices were due to the conversion of agricultural land from food to biofuel crops. Subsidies for the biofuel industry, quoted to be in the region of £5.6–6.1 billion per year (FAO), are believed to incentivise farmers to grow biofuel rather than food crops. However, those supporting biofuels hold the view that better production methods, which will use parts of the plant currently wasted in biofuel production, may be able to increase the efficiency of biofuel production.

Does growing biofuel crops result in more fertiliser and pesticide input?

The amount of fertiliser and pesticide input depends on the crop species grown; one criterion for a suitable biomass crop is that it has a low requirement for nutrients. Switch grass, for example, grows well in poor soil conditions and requires around two-thirds less fertiliser input than a food crop such as maize.

Is there a potential loss of biodiversity?

In some cases, the use of biofuels could increase biodiversity (the number of different species found within a given area), for example, by harvesting woodfuel and then replanting with mixed woodlands. Conversely, the increased use of soybeans for biofuel in the USA has caused soybean production to be increased in South America at the expense of Amazonian rainforest, which has been cut down to give more agricultural land. This has the potential to reduce biodiversity. Also, trees in rainforests help absorb CO_2 (albeit not at the rate of newly planted forests) and so are believed to play a part in offsetting global warming.

Is the energy output greater than the energy input?

The overall energy balance, that is the net energy output compared to the input needed, is dependent on both the species of biomass crop and the type of biofuel being produced. The inputs to a biofuel crop include both the direct costs of growing, such as fertiliser, cultivation, harvest and labour, and the indirect costs, such as storage of the harvested crops. Processing inputs include pre-treatments, processing for energy release and the removal or reuse of residual waste. Ideal crops are being investigated that require low maintenance, need only low nutrients, grow quickly and can tolerate poor soil conditions. Switch grass is one such plant, and interestingly it has been shown that it is only energy efficient if it is used as a pelleted biomass for fuel rather than for bioethanol production.

Do biofuels reduce carbon emissions?

Burning biofuels does release CO_2, but this is CO_2 that has been removed from the atmosphere relatively recently, unlike the carbon in fossil fuels which has been removed from the atmosphere for many millions of years. Hence, biomass energy crops are deemed carbon neutral. However, some argue that nitrous oxide, which is 240 times more powerful as a greenhouse gas than CO_2, is produced in greater quantities during the production of biogas than during the burning of fossil fuels. Also, biofuel production generates CO_2 through the use of agricultural and haulage vehicles for growing and transporting the crop.

This unit is adapted from Open Learn, The Open University, Biofuels course CC BY-NC-SA
www.open.edu/openlearn/science-maths-technology/science/biofuels/

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