And they dispose of their slurry in a “user-friendly” way as they help their governments reach desired non-fossil fuel production targets with biogas from anaerobic digestion (AD). They can also improve their public image at the same time.

In fact it sounds almost too good to be true – a win, win and win again situation as one Danish biogas official described it – and, yes, production of biogas is not all plain sailing.

Challenges which producers will have to face up to include the high capital investment needed, the environmental regulations, which often don’t seem to have evolved quickly enough to cater for the demands of modern high quality AD, and too cautious planning authorities. There may also be problems with other rural residents who claim to be all for renewable energy per se, but oppose biogas plants on principle because they may smell and spoil the tone of the neighbourhood.

One of the best ways to get around the latter, judging by the experience of a few pig producers in the UK and Denmark, is to involve the local community in your proposed biogas project.

Organise public meetings and invite experts in to explain the advanced anaerobic digestion technology, the environmental benefits and the financial rewards. Then, offer to sell shares in the project to the neighbours.

Not only can this help you raise capital for the project, it is also likely to quickly convert the opponents into proponents, once they have heard realise the enormous green potential and they discover that they can also profit from the venture.

Key to making biogas successful

As far as costs go, pig farmers need to know that while slurry provides a stable and useful digester, it does not in itself contain that much energy and the key to profitable biogas production is to combine their slurry with suitable high-energy co-products, such as silage, maize, or food waste to optimise gas production.

In Germany, for example, it is understood that most farmers use about 20% pig slurry and 80% maize as feedstock to feed their on-farm biogas plants.

They calculate that a 200-sow unit can provide enough slurry for a 500kW plant, which is considered commercially viable there, thanks to the generous subsidies they receive for using energy crops, such as maize, as well. The average payback period for these plants is between seven and eight years.

However, those farmers who cannot rely on a steady supply of maize to guarantee biogas production for 365 days a year (essential for a profitable concern), could always look to food waste, which is very high in energy and considered a problem in many developed countries.


It offers great opportunities for farmers who are able to team up local authorities, or nearby fast food outlets. But as a spokesman for a major German biogas plant manufacturer (EnviTec), which has a subsidiary in the UK, pointed out, this means a whole new ball game for producers, because the farm will then be classified as a “waste site,” subject to a host of different regulations.

But he maintained that it could be very profitable for pig producers to collect, or receive, tons of food waste (charging an appropriate gate fee) to mix up with their pig slurry in the AD plant to produce biogas with more oomph to sell off to their national grids.

Payback period

He suggested that the payback period for this type of biogas plant was about four years in Germany and other EU countries, where a premium was paid for green electricity. But he warned that it was a challenging business and could sometimes overtake the farming enterprise, with pig production relegated to a minor role.

Things are certainly going to get more exciting, with even more opportunities opening up for producers as current R & D projects deliver results and technology improves in line with the advances of science.

Already, for example, technicians are talking about recycling the heat from the AD process to provide warmth for offices, or animal housing. And, if the gas is “scrubbed and cleaned,” it can be upgraded and used as a transport fuel in countries where autogas cars or “hybrid” vehicles are growing in popularity.

In addition there is nothing to stop a pig farmer employing other renewable technologies, such as wind turbines and solar panels to increase renewable energy output on their units.

In fact, an increasing number of farmers are finding that the best way to meet their energy needs is to adopt a mix of different renewable techniques, with conventional mains electricity always available as a back-up.

Depending on individual circumstances, this could include biomass boilers, hydropower and underground geothermal technology, as well as AD and we hopefully we can explore the opportunities presented by these other techniques in future issues of Pig International.