Warming to algae and sewage sludge

Many people know that a rippling field of wheat can be turned into fuel to fill up the car. But what about trees, algae, sewage sludge and industrial waste?

They all count as biomass, by-products from forestry and agriculture that can be used to provide heat, electricity and transport fuel. While this hotchpotch of products may not be as eye-catching as other forms of renewable power, such as solar panels and wind turbines, put together they make up the largest source of renewable energy - biomass accounts for 66% of renewables in the EU.

Biomass provides around 4% of the EU’s energy and that figure will grow rapidly if the EU is to meet a stretching target of deriving 20% of its power from green sources by 2020.

For the European Commission, biomass combines the holy grail of growth and jobs with saving the planet. The Commission’s Biomass Action Plan, drawn up in 2005, estimates that Europe will be using 150 million tonnes of oil equivalent (MtOE) of biomass by 2010 and expects plenty of positive spin-offs: a reduction of 209 million tonnes of carbon dioxide (CO2), 250-300,000 new jobs, downward pressure on oil prices, reduced reliance on energy imports and giving Europe an edge in green technologies.

But it could all be too good to be true. Some industry bodies are doubtful about whether there will be enough: Giuliano Grassi, secretary-general at European Biomass Industry Association, thinks that 150 MtOE is not attainable by 2010. And environmentalists are sceptical about the green credentials of some types of biomass. They worry that a careless switch to the ‘wrong’ kind of biomass could put additional pressure on farmland, reduce biodiversity and counteract other environmental goals, such as greener farming or reducing waste. For instance, incinerating waste plastics made from oil (which can be counted as biomass) would do little to cut greenhouse gas emissions. Biofuels also deserve a critical look. Some evidence suggests that first-generation biofuels (bioethanol) can generate more CO2 than petrol. Biofuels are also blamed for rising food prices.

The debate over biofuels has tended to overshadow biomass more generally. But biomass does not have to be bad for the environment. A study by the European Environment Agency has concluded that the EU has "an environmentally compatible biomass potential" of 190 MtOE in 2010 and 295 MtOE in 2030. Professor Gail Taylor, who advises the UK Energy Research Centre, says that using biomass for heat and power is a more efficient use of plant power than bioethanol. She also thinks that agricultural residues and animal waste are underused: "It is a very valuable stream of energy that we are not capturing effectively."

Currently, the UK and Germany are among the biggest users of biomass in the EU, although arguably the record of the Nordic countries and Latvia is better still, as they use more biomass per head. Still, the EU should look to America, which is leading the world in developing so-called bio-refineries. Analogous to an oil refinery, a biorefinery integrates different processes to extract the maximum value from a plant, so converting biomass into fuels, chemicals and power. Taylor imagines that biorefineries will be common in 20 years’ time. "Now, we are very wasteful in our use of plants," she says, citing how wheat is grown for flour and stalks are thrown away; forests are chopped down for timber and the residue is ignored.

In future the full value of a plant will be squeezed out at a biorefinery.

Many people know that a rippling field of wheat can be turned into fuel to fill up the car. But what about trees, algae, sewage sludge and industrial waste?