An overview concerning combined heat and power production: a smart way to improve energy efficiency

Cogeneration power plants simultaneously generate power and usable heat in a single, integrated system, which achieves a degree of overall efficiency that is much greater compared to electricity production alone. This makes better use of energy conversion and reduces greenhouse gas emissions. Combined heat and power production is already relatively common in Europe while it is less common, for example, in the USA. There is great potential for further implementation throughout Europe and worldwide, including in the industrial sector. Major challenges are the short potential distances for the transport of heat and the fact that consumers’ heat demands vary in quantity, mainly due to seasonal effects, and in quality as different applications require different temperature levels. Cleaner production schemes offer suitable frameworks to foster uptake of combined heat and power production by industry, in particular by small and medium sized enterprises

Dry Digestion of Organic Residues

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Oat husks in anaerobic digestion

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BIOLOGICAL METABOLITES RECOVERY FROM BEVERAGE PRODUCTION SOLID RESIDUES THROUGH ACIDOGENIC FERMENTATION

Acidogenic fermentation was applied to evaluate the potential recovery of biological monomers as precursors in bio-plastic production. Three residual organic substrates from high-volume beverage sectors (coffee, orange juice, beer) were assessed: spent coffee grounds (SCG), orange peels (OP), and brewers\u2019 spent grains (BSG). Batch fermentation tests were set up. SCG and OP were studied as single substrates and combined to evaluate yields of target monomers (volatile fatty acids, ethanol, lactate) and to reveal interactions between the matrixes. NaOH pre-treatment was applied to SCG to enhance disruption of the lignocellulosic cell wall. BSG was studied without pre-treatment and following acid or alkaline pre-treatment, with acidogenic fermentation being initiated with two different initial pH values (7; 9). Acetogenic fermentation was achieved with all substrates, although with different yields of target monomers. In terms of total biological metabolite production, following alkaline pre-treatment, OP and BSG, both fermented at an initial pH 9, showed the best performance, yielding 62.6 g and 62.0 g target monomers per litre substrate. For all substrates, acetic and butyric acids were the most abundant products. In the case of OP fermentation, butyrate accounted for 57% (35.8 g/L) of the total. The BSG test with the highest total yield also achieved the highest acetate yield (36.7 g/L). The results confirm that OP and BSG should be considered a priority sustainable feedstock for the supply of biological monomers, particularly if polyhydroxyalkanoates are to be produced. SCG are better suited to aceto-oriented approaches, such as the production of polyvinyl acetat