Abstract
Ash-related issues from a considerable amount of alkali and alkaline earth metal species in biochar are major obstacles to the widespread application of biomass in thermoelectric plants. In this study, food wastes were converted into biochar through pyrolysis at 450 °C or 500 °C and four different demineralization approaches, using deionized water, citric acid, nitric acid, and CO2 saturated water. The chemical properties of the resulting biochars were investigated, including proximate analysis, concentrations of inorganic species in biochar and ash, and the crystalline structure. All demineralization treatments produced food waste biochar with sufficient calorific value (>4000 kcal/kg) and a chlorine concentration <0.5%. Among the inorganic species in biochar, Na and K exhibited a significantly higher removal rate through demineralization, which ranged from 54.1%–85.6% and 53.6%–89.9%, respectively; the removal rates of Ca and Mg were lower than 50.0%. The demineralization method was more critical than the pyrolysis temperature in the removal of alkali and alkaline earth metals. Especially, the lower slagging and fouling tendency was expected for the biochar demineralized with citric acid. Our results suggested that food waste biochar pyrolyzed at 500 °C and demineralized with citric acid is a promising co-firing material for electric power generation in thermoelectric power plants.
Highlights
With mounting concern over the environmental burden of conventional energy resources, biomass is the focus of alternative fossil fuels
As the pyrolysis temperature increased from 450 ◦ C to 500 ◦ C, the contents of ash and fixed carbon in the biochar before demineralization increased by
The higher pyrolysis temperature increased the efficiency of demineralization, resulting in a positive effect on ash reduction
Summary
With mounting concern over the environmental burden of conventional energy resources, biomass is the focus of alternative fossil fuels. Among various sources of biomass, food waste is regarded as an untapped energy resource with a large currently generating and potential future volume and high carbon content [6]. Food waste does not compete with food crops nor does it cause land clearing issues. These characteristics of food waste qualify for sustainable biomass [7]. In the Republic of Korea, approximately 97% of food waste is recycled, most of which is processed into composting and animal feed. Composting and animal feed using food waste are not favored due to the high chlorine content in food waste and the low quality of the final product
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