The work carried out during the Ph.D. project is part of the Danish Energy Authority funded research project called PSO REnescience and is focussed on studying the enzymatic hydrolysis and liquefaction of waste biomass. The purpose of studying the liquefaction of waste biomass is uniform slurry generation for subsequent biogas production.
Municipal solid waste (MSW) is produced in large amounts every year in the developed part of the world. The household waste composition varies between geographical areas and between seasons. However the overall content of organic and degradable material is rather constant between 50 - 60 % wet weight and therefore holds a potential for bioenergy production. The degradable fraction has positive effects for anaerobic digestion when evaluated to desired parameters of anaerobic digestion plants. Wanted parameters are: 1) high organic content (high volatile solid content), 2) low ash and xenobiotic content, 3) high gas yield, 4) volume (produced), 5) dependable distribution and 6) low competition with other end-user technologies.
MSW is a complex substrate comprising both degradable and non-degradable material being metal, plastic, glass, building waste etc. Different separation techniques are used and developed for the purpose of separating degradable and non-degradable fractions. Most of these techniques involve mechanical treatment including severe shredding for downstream separation. Mechanical separation have a low separation power loosing between 30 - 50 % of the organic and degradable material.
Source sorting is another way of collecting the household waste in its respective fractions. However, this separation technique is hard to enforce and expensive.
Future waste management calls for novel and efficient technologies for the separation of unsorted MSW in order to utilise waste constituents in a refined and sustainable way. The process described in the present work includes a pretreatment and an enzymatic liquefaction, which continuously treats unsorted MSW. The work involve evaluation of 1) different enzymes and their performance on liquefaction of modelled waste simulating Danish household waste in composition and weight, 2) evaluating the performance of best enzyme candidates on original waste with and without
additional additives, 3) measuring the biogas potential of liquefied waste and comparing the results with the biogas potential of untreated waste