• Energy Research
• 6. Clean water close

Tests with vine pruning and rice husks were carried out in a demonstrative downdraft gasifier (350 kW), to prove the reactor operability, quantify the plant efficiency, and thus extend the range of potential energy feedstocks. Pressure drops, syngas flow rate and composition were monitored to study the material and energy balances, and performance indexes. Interesting results were obtained for vine pruning (syngas heating value 5.7 MJ/m(3), equivalent ratio 0.26, cold gas efficiency 65%, power efficiency 21%), while poorer values were obtained for rice husks (syngas heating value 2.5-3.8 MJ/m(3), equivalent ratio 0.4, cold gas efficiency 31-42%, power efficiency 10-13%). The work contains also a comparison with previous results (wood pellets, corn cobs, Miscanthus) for defining an operating diagram, based on material density and particle size and shape, and the critical zones (reactor obstruction, bridging, no bed buildup, combustion regime).

Bio-oils were produced from bench-scale slow-pyrolysis of three different biomass samples (corn stalks, poplar and switchgrass). Experimental protocols were developed and applied in order to screen their chemical composition. Several hazardous compounds were detected in the bio-oil samples analysed, including phenols, furans and polycyclic aromatic hydrocarbons. A procedure was outlined and applied to the assessment of toxicological and carcinogenic hazards of the bio-oils. The following hazardous properties were considered: acute toxicity; ecotoxicity; chronic toxicity; carcinogenicity. Parameters related to these properties were quantified for each component identified in the bio-oils and overall values were estimated for the bio-oils. The hazard screening carried out for the three bio-oils considered suggested that: (i) hazards to human health could be associated with chronic exposures to the bio-oils; (ii) acute toxic effects on humans and eco-toxic effects on aquatic ecosystems could also be possible in the case of loss of containment; and (iii) bio-oils may present a marginal potential carcinogenicity. The approach outlined allows the collection of screening information on the potential hazards posed by the bio-oils. This can be particularly useful when limited time and analytical resources reduce the possibility to obtain detailed specific experimental data.