Metanpotential för alger och bioslam blandat med pappersfiber

Sammanfattning: In this thesis the methane gas potential of three different substrates, two algaes Saccharina latissima and Laminaria digitata and biosludge mixed with paper fiber was studied. This was done by batch experiments in a laboratory environment to examine the gas production and composition of the produced gas. Biogas production is a complex anaerobic digestion process in which various microorganisms decompose the substrate in steps and at the end produce biogas and a residue. Many factors affect the production of gas, for example the substrate content, temperature and pH in the digester. The analysis of methane potential were divided into two experiments. In experiment 1 substrates were digested along with inoculum from Växjö waste water treatment plant in a temperature of about 37 ˚C. In experiment 2 substrates were digested along with inoculum from Kalmar Biogas AB at about 52 ˚C. Both experiments contained 15 bottles each with three replicates for each substrate: only inoculum, inoculum + Algae 1 (Saccharina latissima), inoculum + Algae 2 (Laminaria digitata), inoculum + Paper (biosolids mixed with paper fiber), inoculum + Reference (Cellulose). The inoculum and the reference were running to assess the quality of the inoculum. Mixtures between the inoculum and the substrate was first set to 5:1 and then 4:1, based on the material's VS-concentration. All experiments went on until gas production was minimal. For experiment 1 ,with the ratio of 5:1, the end results of the accumulated methane for Algae 1, Algae 2, Paper and Reference were 315, 313, 88 and 381 Nml CH4/g VS substrate respetively. The batch with inoculum + Paper was ended after seven days because the difference between inoculum + Paper and only inoculum was small. In experiment 1, with a ratio of 4:1, inoculum + Reference and inoculum batches were not prepared mainly because of lack of space.The batch with only inoculum was assumed to give the same results as in experiment 1, with the ratio of 5:1. The end results of the accumulated methane for Algae 1, Algae 2 and Paper were: 199, 214 and 41 Nml/g VS substrate repectively For experiment 2, with the ratio of 5:1, the end results of accumulated methane for Algae 1, Algae 2, Paper and Reference were: 191, 183, 33, 243 Nml/g VS substrate respectively In experiment 2, with the ratio 4:1, the end result of accumulated methane for Algae 1, Algea 2, Paper and Reference were: 288, 179, 18, 337 Nml/g VS substrate respectively.