This leads to a range of significant environmental and societal benefits, including:
1.increased GHG savings from displacement of fossil fuels;
2.reduced use of artificial fertilisers, displacing greater amounts of GHG
3.reduced odour and flies at livestock units that adopt biogas
4. reduced diffuse pollution and improved water quality from better management of farm wastes.

The climate change (and economic) benefits of the process are improved when both heat and electricity are captured. In Germany, many biogas plants are fed with maize, but other high energy crops which use less fertiliser may show better returns. Biogas can be developed at farm scale, using simple equipment and farm based inputs, or on a larger scale as at Bedfordia Farms where the economics are supported by charging gate fees for treating food wastes from local businesses.

Biofuels

There is currently considerable controversy about the true benefits of biofuels (now referred to by some campaigners as agro-fuels), in terms of climate change,13 and about the potential to replace more than about 10% of road fuels from this source. However, the UK is committed to implementing a road-transport biofuels obligation (RTFO15) under which there would be a mandatory inclusion of 5% of fuels from renewable sources by 2010, and the reduced excise duty16 remains in place.

Campaigners often fail to distinguish between biofuels from different sources, which have very different energy ratios and effects on climate change.Whereas some biofuels involve land use change, which may put increased pressure on biodiversity, most of those actually used in the UK produce substantially more energy than was consumed in their production.

Assuming oilseed rape yields of 5.5 tonnes per hectare, and biodiesel yields of 415 kg to 470 kg per tonne of rapeseed, biodiesel production would be about 1.3 to 1.5 tonnes per hectare.

At current oil prices and rapeseed prices, it would be difficult to secure a margin from biodiesel produced from oilseeds, since in the UK biodiesel has to be sold at a discount to secure a market.Most commercially available biodiesel in the UK is produced from waste vegetable oils. However, it would in theory be possible to secure a margin if a premium price could be secured, probably from a distributor (with fuel depots) looking to enhance the green credentials of their product.

It is also important to consider biofuels which can be produced from wastes. The biofuel from waste with perhaps the greatest potential is biomethane, produced by refining biogas from anaerobic digestion plants.

In addition, in Australia the process of pyrolysis (burning at high temperatures in the absence of air20) is used to produce road quality diesel from waste plastics. One of the by-products of biomass pyrolysis is biochar (or agri-charr) which has potential to lock up significant quantities of carbon dioxide in soils, thus contributing to climate change mitigation.

There are other potential sources of biomass, for instance the planned £40m distillery plant in Roseisle on Speyside will halve its fuel bills by burning dried barley from the ‘spent wash’, a by-product of the distillation process, to generate heat.

Research is now underway in Northern Ireland to produce biofuels from seaweed.