Abstract
Large amounts of agricultural residues are produced annually in the UK alone, which presents a significant biomass energy resource. It has limited availability in briquetted form in the UK but is widely used, particularly in Asia. The aim of this work is to assess the emission from briquetted agricultural residues to wood fuel, including commercial wood briquettes, when utilised in a 5 kW domestic heating stove. Other straw-type materials, sugarcane bagasse, Miscanthus, were also investigated. The combustion behaviour depended on the chemical and physical nature of the briquettes. Results indicate that fuel choice is an important consideration for emission reduction. Fuel-N directly correlates to emitted NOx and all the fuels studied had NOx emissions below the EU regulation limit. While agricultural residues can be relatively high in Cl and S, there is evidence of in-situ capture of HCl and SO2 by calcium salts in the fuel ash. Particulate emissions correlate with the volatile matter in the fuel, but also are influenced by the quality/durability of the briquette. The briquettes performed well compared to wood logs, and while there is a fuel-type influence on emissions, it is also clear that briquettes from optimised manufacture can be lower emitting than wood logs.
Highlights
In many countries' biomass fuels, such as wood have replaced coal for small domestic stoves in a move to decarbonisation and because it is often a convenient alternative
The use of non-woody residues such as herbaceous materials and agricultural residues is another alternative [1], but these fuels tend to be of a lower quality, and, in the UK few are approved for use in smokeless areas [2]
In recent years there has been an increasing use of these low-grade biomass fuels more widely and this paper seeks to identify the performance of briquettes manufactured from agricultural residues (AgR) and wood residues, which could be a cost-effective alternative fuel to wood logs
Summary
In many countries' biomass fuels, such as wood have replaced coal for small domestic stoves in a move to decarbonisation and because it is often a convenient alternative. Volatile salts (such as K-salts) condense into the emitted particulate, they have not demon strated cytotoxicity [4,9], and those in the solid phase can affect the melting temperature of the ash This has been a known issue in large scale biomass heat and power generation for many years, but, for space heaters, there has been few cases reported of slagging, fouling, corro sion and bed agglomeration in small scale systems because of the lower combustion temperatures. This is not the case for pellet boilers, where ash agglomeration can be a serious problem during periods of prolonged use at high load because of the higher operating tempera tures. Agronomy may be important here as well [14,15,16]
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