Where wood processing residues are insufficient to meet the fuel demand for a biomass fuelled boiler then alternative fuel supplies need to be considered. One fuel to consider is forest residues at landings and skid sites within the forests. Providing factors affecting supply are appropriately evaluated then these forest residues can be a cost effective fuel.
The following link describes a hypothetical assessment of the potential supply and cost of forest residues to a bioenergy plant. Wood Processing Residues As Fuel [PDF 112kb]
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Wood boiler fuel - Payment by energy versus weight – Case study
This study determines the effects of moving from a payment system based on weight to a payment system based on energy‑content at a large industrial site, using woody biomass as a fuel source. The benefit of paying by energy content would be that the purchaser could predict how much fuel he would need to buy to meet a specific energy demand. An energy-based payment system could also lead to delivery of better quality fuel (i.e. drier and cleaner), thus helping to overcome one of the barriers to increased use of wood residues as a fuel. Paying by energy content avoids the issue of over- or under-payment, which can happen with weight-based payment systems... read case study.
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Woody biomass for boiler fuel - Guidelines for payment by energy content
A payment system based on energy content is one method of ensuring a high value fuel, which is paid for in a manner fair to both buyer and seller. The higher the quality of the fuel, the higher the energy content, the higher the value to both seller and purchaser. This report makes practical recommendations on how to move from a weight-only system to a simple weight-by-moisture content system... read case study.
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Forest residue recovery study - Hogging direct to truck versus hogging to ground - fibre loss and cost issues
The Wood Energy Programme Engineering Solutions Phase I study identified a number of potential opportunities to improve the efficiency of forest residue derived fuel delivery. One of these was to reduce fibre loss during hogging and loading.
Current practice is for the hogger out-feed to discharge hogged material directly onto the ground, and trucks are loaded from a stockpile of hogged material with a front-end loader. The goal of this study was to determine the fibre loss associated with hogging onto the ground and compare this with hogging directly into a truck. Fibre loss in the order of 4% was found in the hog-to-ground system.
The potential differences in trucking costs were also examined as hogging into a truck entails increased loading time, and the extra cost of the truck and driver may or may not be offset by the reduced fibre loss... read case study.
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Turning forestry waste into renewable energy
18 July, 2007
In New Zealand, residue from forest harvesting is usually left to decompose. Forestry practices and environmental conditions in New Zealand have made it difficult to efficiently extract and use forestry residue. However machinery has been developed that allows processing of forest residue on-site, in local conditions. These machines, called hoggers, produce processed wood used to fire boilers.
In the central North Island, forest residue is now being collected from several forests, processed on-site into boiler fuel by hoggers and delivered to pulp mills. The practice is expected to become more widespread as fossil fuels and electricity become more expensive.
This case study reviews three hoggers’ performances and identifies the key drivers of efficiency.
Read the full case study (PDF)