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Biomass energy for heating is going to be part of the spectrum of renewable energy sources. However, biomass combustion produces emissions of various pollutants with negative effects at both local and global scales. To reduce some of the locally important pollutant load, thermally treated biomass fuels may offer a partial solution. In this study, two biomass feedstocks, i.e., spruce chips and rapeseed straw, were thermally treated at 300 °C to produce biochars. Subsequently, both original materials and biochars were burned in a 25 kW retort combustion device. In both cases, the biochar showed lower emissions of carbon monoxide and nitrogen oxides, usually almost across the whole range of tested combustion conditions. In total, for the emission production per unit of net calorific value, the spruce biochar showed reductions in CO and NOx productions of 10.8% and 14.5%, respectively. More importantly, in rapeseed straw biochar, the difference was more pronounced. The total production was reduced by 28% and 42%, again in CO and NOx emissions, respectively. [ABSTRACT FROM AUTHOR]

The use of grape residues as a renewable energy source for combustion presents various problems. One of these is the excessive production of carbon monoxide and nitrogen oxides. Analyses and combustion tests were performed on white and red grape pomace as well as grape stems. To verify the possibility of a reduction in emissions, straw of Miscanthus sinensis was added to mixtures with red grape pomace. Emission concentrations of carbon monoxide and nitrogen oxides were determined on a grate combustion device with a nominal thermal output of 8 kW under steady-state conditions. In addition to these emission concentrations, the excess air factor and the flue gas temperature were monitored. The results show a high energy content in grape residues. In red grape pomace, the gross calorific value of dry matter reached 22.17 MJ kg−1. Unfavourable properties included high ash and nitrogen contents. During combustion tests on all types of grape residue, the emission concentrations of carbon monoxide were above the legal limit for the combustion of solid fuels. The addition of Miscanthus straw improved the behaviour during combustion. The maximum content of grape pomace in the mixture capable of meeting legislative emission requirements was 50% wt. [ABSTRACT FROM AUTHOR]

• Spruce, pine and larch cones were compared to spruce wood. • The cones had comparable energy content to spruce wood. • Pine cones showed the lowest emission levels, while larch cones had the highest. The aim of the research was to determine selected fuel properties and basic emission characteristics of briquettes made from cones of three tree species: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies H. Karst.) and European larch (Larix decidua Mill.). Combustion tests were carried out under stabilized operating conditions (heat output, excess air coefficient) on a grate-fired combustion device. The elemental composition of the cone samples and the heating values were determined. The briquettes were evaluated in terms of carbon monoxide and nitrogen oxide emission concentrations depending on the excess air factor and the flue gas temperature. The composition and energy content of the cone materials were comparable to wood. In the dry state, the ash content was between 0.69 and 1.29% wt. and the lower heating values between 18.77 and 19.58 MJ·kg−1. This suggests favourable properties for use as a solid biofuel. However, during combustion all cone briquettes achieved higher emission levels of nitrogen oxides as well as carbon monoxide compared to spruce wood briquettes. Larch cone briquettes were consistently the highest in emissions which reached concentrations of carbon monoxide in flue gas up to 3500 mg·m−3. On the other hand, spruce and pine cone briquettes kept concentrations of carbon monoxide below 2000 mg·m−3 at excess air coefficients under 2.4. The amount of excess air significantly influenced the temperature of the exhaust gas, which was maintained above 300 °C during the tests. In the tested areas and the excess air coefficients the concentrations of nitrogen oxides did not exceed 200 mg·m−3 and were low for all samples. [ABSTRACT FROM AUTHOR]