In a paper just released in the leading bioenergy journal Global Change Biology Bioenergy, researchers from Bangor University and the Thünen Institute in Germany conclude that crop-biogas and liquid biofuels are at best inefficient options for greenhouse gas (GHG) mitigation, per hectare of land used and per £ public subsidy required. At worst these options could actually lead to higher global GHG emissions owing to indirect land use change caused by displacement of food production (...) Bio-electricity feed-in-tariffs (FiTs) are encouraging the use of crops to produce biogas in large scale anaerobic digestion plants, whilst mandatory biofuel blend targets are driving the production of liquid biofuels from food crops. There is concern that these policy measures do not target the most sustainable bioenergy options to reduce dependence on polluting fossil fuels, and to reduce GHG emissions that contribute to climate change (...) Dr David Styles, who led the research, commented: “Whilst subsidies are necessary to correct for market failure and develop vital renewable energy sources, it would seem sensible to link such subsidies with environmental sustainability criteria to ensure that they efficiently contribute to overall net public good. Our results highlight the importance of applying life cycle assessment to comprehensively evaluate the environmental sustainability of bioenergy options, capturing hotspots such as indirect land use change associated with food crop displacement, the climate effect of bio-methane leakage, and ammonia emissions arising from digestate storage and spreading.”  Styles, D., Gibbons, J., Williams, A.P., Dauber, J., Stichnothe, H., Urban, B., Chadwick, D., Jones, D.L., 2015. Consequential life cycle assessment of biogas, biofuel and biomass energy options within an arable crop rotation. Global Change Biology Bioenergy: doi 10.1111/gcbb.12246

The new renewable energy law (EEG 2014) came into force in Germany on 1 August 2014 and marks a turnaround for biogas. Future production will be much less geared to using energy crops. One of the new law’s aims is to reduce the financial cost of energy transition by slowing the growth of the most expensive electricity- generating sectors. Solid biomass and biogas find themselves in the line of fire. One of the main measures of the new law affecting biogas is the withdrawal of the premium for using energy crops (NawaRo-Bonus), to encourage the use of organic and farming waste. Another major upset is that to limit the remuneration of biogas installations, biogas plants with capacity in excess of 100 kW will henceforth only be eligible for financial support of up to 50% of their nominal installation capacity. The new payment system is still more generous to small installations that transform agricultural waste. The setting of the 100-MW ceiling on new biogas installations will result in a sharp drop in their number from 2015 onwards. From EurObserv’ER Biogas Barometer, November 2, 2014

“Biogas is now going the same way [than biodiesel]. Provide the money to do the right thing and if you're not careful it will be used to do the wrong thing.

Part of the problem is that there's not enough money on offer to make the conversion of waste alone economically viable. That's because the yields of gas are often quite low. For example, slurry from cattle and pigs produces only 15 to 25 cubic metres (m3) of biogas per tonne of material. Purpose-grown crops are much more productive. Grass silage produces 160-200m3 per tonne, while silage made from maize (which in the US is called corn) generates 200-220m3, and potatoes 280-400m3.

Economic modelling commissioned by the government tested eight different mixes with which farmers could feed an anaerobic digester, to try to work out which were profitable. All of them included grass, wheat, maize or potatoes, and in some cases the models specified a higher tonnage of these specially grown crops than the waste the digesters are supposed to process. As maize has both a high yield per hectare and a high yield of biogas per tonne, it has become what the farming press calls the biogas "core crop". There could scarcely be a better formula for subverting everything biogas is supposed to achieve.

(...) If you want to know where we might be heading, take a look at Germany. Two years ago Der Spiegel reported:

"Subsidies for the biogas industry have led to entire regions of the country being covered by the crop … Plans called for transforming Germany into a bio-wonderland by peppering it with numerous small eco-power plants. What resulted was a revolution in the fields, a subsidised gold rush – and an ecological disaster. Corn [maize] is now being grown on 810,000 hectares in Germany."

As a result, "for the first time in 25 years, Germany couldn't produce enough grain to meet its own needs."

(...) In other words, it's the biodiesel story, all over again. Because the anaerobic digestion of waste food and slurry makes sense, I don't want to see a biogas moratorium imposed. But I would like to see a ban on the use of all purpose-grown feedstocks. To make biogas viable, this ban would have to be accompanied by an increase in the subsidies available for converting waste. Yes, that means extra expense, but it's got to be a better deal than trashing the food supply, the soil, the rivers and our living rooms – all in the name of protecting the planet.” From How a false solution to climate change is damaging the natural world  by George Monbiot, The Guardian, March 14, 2014