Biofuels Production and Greenhouse Gases Emissions


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Greenhouse Gases and CO2: Emissions

One of the points raised by the authors is that, when greenhouse gas emissions associated with biofuels are calculated, some key contributions are either not taken into account properly or not taken into account at all. The offset of CO2 emission due to the growth of biomass, for instance, is calculated incorrectly.

In the majority of cases, the land used for biomass cultivation would be used in any case, either to grow something else or to grow the same plants for another use (i.e. crops for food consumption). The absorption of CO2 by the biomass, therefore, does not give an “extra” CO2 absorption, since the absorption would take place anyway, even without the biomass production. When the biomass is burned, however, it still generates CO2, resulting in a net greenhouse increase, rather than a net offset.

Moreover, biofuels combustion is, on average, less effective than the combustion of fossil fuels. This means that, for the same energy produced, more CO2 will be emitted from biofuels than from fossil fuels. This, again, is environmentalists do not often consider when calculating the overall greenhouse gases emissions.

Nitrogen coming from fertilizers can convert to N2O, a greenhouse gas. Photo by Andy Beecroft.

Climate Change:The Effect of the Fertilizers on the Environment

Consider another feature of biofuel production – the possible emissions of greenhouse gases from the fertilizers used to support the growth of biofuel products. Most of the fertilizers contain nitrogen (N), which could react with oxygen to produce N2O, a molecule with a greenhouse power about 300 times greater than CO2.

In the production of crops, only 40% of the fertilizer is actually absorbed by the plants; the unused fertilizer could, therefore, generate N2O. The emission of this greenhouse gas has been taken into account in some theoretical models simulating biocrop growth, but, according to the authors of this research, the real contribution is much higher than that considered in the models – the real effect on the greenhouse gas emission is higher than expected, and not negligible.

Biofuels vs. Fossil Fuels: A Complex Topic

This study, performed by Professors Searchinger and Smith, confirms once more that the topic of greenhouse gas reduction and biofuel production is very complex; many aspects have to be considered to have a complete picture. Only with a proper knowledge of the real impact that biofuels have on the environment can effective policies be developed and placed in action.

Although, as Prof. Searchinger told Decoded Science, this paper is “largely a repeat of work that both I and Keith Smith have done before,” and they were simply asked to summarize the arguments made in two earlier papers, the combination of the earlier research in this study is still significant. According to Professor Searchinger, in his paper’s conclusion, “attention should be focused on waste-feedstock or high-yielding bioenergy crops with low energy demand.”


K.A. Smith, et al. Crop-based biofuels and associated environmental concerns. Global Change and Biology – Bioenergy, doi: 10.1111/j.1757-1707.2012.01182.x (2012).

Greenpeace. Fueling the Flames. (2011). Accessed July 1, 2012.

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