Abstract
Combustion of waste wood can cause slagging, fouling and corrosion which lead to boiler failure, affecting the energy efficiency and the lifetime of the power plant. Additivation with mineral and sulfur containing additives during waste wood combustion could potentially reduce these problems. This study aims at understanding the environmental impacts of using additives to improve the operational performance of waste wood combustion. The environmental profiles of four energy plants (producing heat and/or power), located in different European countries (Poland, Austria, Sweden and Germany), were investigated through a consequential life cycle assessment (LCA). The four energy plants are all fueled by waste wood and/or residues. This analysis explored the influences of applying different additives strategies in the four power plants, different wood fuel mixes and resulting direct emissions, to the total life cycle environmental impacts of heat and power generated. The impacts on climate change, acidification, particulate matter, freshwater eutrophication, human toxicity and cumulative energy demand were calculated, considering 1 GJ of exergy as functional unit. Primary data for the operation without additives were collected from the power plant operators, and emission data for the additives scenarios were collected from onsite measurements. A sensitivity analysis was conducted on the expected increase of energy efficiency. The analysis indicated that the use of gypsum waste, halloysite and coal fly ash decreases the environmental impacts of heat and electricity produced (average of 12% decrease in all impacts studied, and a maximum decrease of 121%). The decrease of impacts is mainly a consequence of the increase of energy generation that avoids the use of more polluting marginal technologies. However, impacts on acidification may increase (up to 120% increase) under the absence of appropriate flue gas cleaning systems. Halloysite was the additive presenting the highest benefits.
Highlights
The use of biomass as sustainable energy source has been subject of debate over the last years, both in the public (Van Hilst et al, 2017) and scientific domains (Agostini et al, 2019)
As part of the REFAWOOD project, this study explores how the quantitative environmental impacts of waste wood combustion could be influenced by different fuel compositions, energy plant characteristics, ashes management, and in particular, additives strategies
The results indicate different environmental profiles per functional unit for each power plant, due to their different fuel characteristics, transportation distances, operation parameters and combustion emissions
Summary
The use of biomass as sustainable energy source has been subject of debate over the last years, both in the public (Van Hilst et al, 2017) and scientific domains (Agostini et al, 2019). Waste wood is gaining interest as a bioenergy feedstock that could avoid land competition, reduce greenhouse gas (GHG) emissions, and contribute to meet the renewable energy targets of the European Renewable Energy Directive (EC, 2018). This last issue is especially relevant in the heating and cooling sector, whose share of renewable sources is increasing at a slower rate than in the electricity sector (3% against 8% in the period 2010e2015) (Bauknecht et al, 2017). Post-consumer waste wood originates from wood products whose lifetime has finished and are discarded as waste This wood waste has a limited potential for material recovery due to contaminants. Waste wood combustion in combined heat and power (CHP) plants is becoming
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