“Dry Roast” Biomass could be more easily used by UK power stations

UK power stations are using biomass alongside coal to produce energy and reduce their carbon footprint, but if it were pre-dried it would be a more useful energy source, according to researchers at the University of Leeds.

Using biomass to produce energy is being explored by many players in the energy industry trying to find more sustainable ways to operate and also to reduce carbon footprints. There are practical difficulties with using biomass though; one is the moisture in the biomass. This moisture adds to the weight and mass, which increases transport costs and the moisture also makes biomass more difficult to burn. Because of the moisture storage becomes a problem as the material starts to rot. Finally, the process used to grind coal before burning isn’t an ideal way to grind biomass which is very variable in consistency.

Torrefaction is proposed as a solution; it is a roasting process where the mass is heated to around 300°C in the absence of oxygen. It produces dry biomass that can be more easily ground into fuel which is not subject to the problems that wet biomass has. If torrefaction were to be done at the production site, it would save transport costs and when it arrived at the power plant it would burn more uniformly, more cleanly and more efficiently. Replacing coal with biomass becomes more attractive if it is processed this way.

University of Leeds' School of Process, Environmental and Materials Engineering, Professor Jenny Jones:

"If we can show that torrefaction is feasible on an industrial scale then we would hope to end up with a demonstration plant here in the UK. We already know that many more famers would be interested in growing energy crops on areas of poorer quality soil if the economic barriers were lowered and the power companies could use more biomass without losing out financially."

"We do not want farmers to have to choose between planting a field of wheat or barley and a field of willow. Ultimately, this is all about providing a secure energy supply for the future and one that is sustainable on all levels. "

Researchers at the University of Leeds are looking at the potential to scale up and commercialise torrefaction; it is important for it to be cost competitive with using coal and the whole life cycle analysis is a must; mining coal is energy intensive but how does this balance with combined farming and torrefaction? There are other impacts of the process that need to be considered, like the safety and environmental impacts.