Sustainable gas from ’roasted’ wood is a feasible option

’Roast’ hardwood at relatively low temperatures and then gasify it. Dutch chemical engineer Mark Prins has shown that this is an efficient means of producing sustainable energy. The gas produced can be used for the production of electricity, fuels and/or chemicals.

Prins followed a thermodynamic approach to investigate how biomass could be gasified as efficiently as possible. He developed a concept which combines two techniques: torrefaction (’roasting’ at a temperature of 250 to 300°C) and gasification. Roasting increases the calorific value of the biomass and decreases its humidity content. This considerably improves the properties of the biomass for gasification. At practical gasification temperatures between 900 and 1200°C, roasted biomass becomes less ’over-oxidised’ than untreated biomass, which is favourable for the efficiency of the process. Efficient processes of this type need to be further developed if sustainable energy is to become a feasible option.

Experimental research into the torrefaction of biomass was carried out in cooperation with the Netherlands Energy Research Foundation (ECN) and Shell Global Solutions, with the support of the Sustainable Energy Foundation (SDE). The process is more suitable for hardwood (e.g. beech and willow) and straw, than for softwood (e.g. larch), due to the composition of the hemi-cellulose fraction in the wood. During his research, Prins developed a model to describe the weight loss of the wood and he also analysed the products formed.

Public acceptance

Prins focussed on the technological development of the gasification process. However, he acknowledges that other non-technical aspects are important for further implementing this type of process: in particular the cost and availability of biomass and the social acceptance of this energy source. These aspects are also being investigated in the biomass programme at Eindhoven University of Technology. For example, it has been found that at present, the public thinks using waste materials as an energy source is more sustainable than using cultivated crops and wood.

The research formed part of the programme ’Biomass as a sustainable energy source: environmental load, cost-effectiveness and public acceptance’ that is being financed by NWO/SenterNovem Stimulation Programme Energy research. This programme is a joint initiative of SenterNovem and the Social Sciences Research Council. Its aim is to develop knowledge in the natural sciences and humanities concerning the transition towards a sustainable supply of energy.