Pellet Production

The demand for biofuel pellets has increased considerably in recent years, causing shortage of the traditional raw materials sawdust and wood shavings. In this study, the costs and energy requirements for the production of pellets from agricultural raw materials were analysed. The materials studied were Salix, reed canary grass, hemp, straw, screenings, rape-seed meal, rape cake and distiller’s waste. Four production scales were analysed, having an annual output of 80,000, 8000, 800 and 80 tonnes of pellets per year. It was concluded that the raw materials of greatest interest were Salix and reed canary grass. They had competitive raw material costs and acceptable fuel properties and could be mixed with sawdust in existing large-scale pelleting factories. Straw had low production costs but can cause serious ash-related problems and should, as also is the case for screenings, be avoided in small-scale burners. Hemp had high raw material costs and is of less commercial interest, while distiller’s waste, rape-seed meal and rape cake had higher alternative values when used as protein feed. The scale of production had a crucial influence on production costs. The machinery was used much more efficiently in large-scale plants, resulting in clear cost savings. Small-scale pelleting, both static and mobile, required cheap raw materials, low labour costs and long utilisation times to be profitable. In most cases, briquetting would be more commercially viable. The energy use in manufacturing pellets from air-dried crops was generally no higher than when moist sawdust was used as the raw material.

To prepare the raw materials is the first thing when we make wood pellet. For small wood pellet plant, the raw materials quantity is not much. If the wood pellet is for personal use, the raw materials are normally the crop waste in the farmland. If the small pellet plant produce wood pellet for commercial purpose, the raw materials are normally the wood shavings collected from saw mill nearby. But for large wood pellet plant, the preparation of raw material become a serious problem which impact the pellet plant capacity directly. As the demand of raw materials for a large pellet plant is massive, the wood shaving quantity of a saw mill is not enough for a large pellet plant. Therefore, a large pellet plant usually use wood logs and branches as raw materials, or to find some saw mills and sign a long term wood shavings supply contract with them.