Biomasa z hmyzu jako alternativní substrát pro výrobu bioplynu a jeho následné čištění pomocí kondenzující vodní membrány

Abstract

The dissertation thesis focuses on assessing the possibility of processing insect biomass and waste from insect farming using anaerobic digestion, followed by designing equipment for biogas treatment to biomethane. Several tests of the biochemical methane potential (BMP) of the mentioned materials were conducted, including influence examination of their organic loading on the overall biogas production, specifically CH4. During 40-day batch BMP tests of biogas production from mealworm larvae and black soldier fly larvae it was confirmed that these materials have relatively high biogas and CH4 yields. It was found that the highest specific biogas production and CH4 production was obtained from the mealworm larvae test. In both tested insect larvae, the highest specific productions were achieved at the lowest loading, consistent with the theoretical expectation of the lowest concentrations regarding inhibition or toxicity of problematic substances. During thirty five-day tests of mesophilic batch anaerobic digestion, biogas and CH4 production was measured for 4 types of insect farming waste. The tested samples showed that waste from these 4 most commonly produced insect species are relatively easily degradable materials with moderately high biogas and CH4 production. Based on the results of the tests, the substrate with the highest risk of anaerobic process inhibition - mealworm larvae - was subjected to a long-term semicontinuous co-fermentation test with corn silage. The semicontinuous test provided basic information about the co-fermentation of mealworm larvae with corn silage. The second part of the dissertation focuses on the purification of raw biogas to natural gas level using a new technology of water separation with a water swollen composite membrane. The experiments were conducted to separate biogas components at different temperatures and pressures, and based on the results of volumetric balances, the usability of the selected roll-filtration module for biogas upgrade in operational scale was assessed. In a single-stage separation of synthetic biogas components with one filtration module, at an input gas pressure of 300 kPa, a steady state was approached after 120 minutes. The result of the separation was a retentate with 98 vol. % CH4 and a CH4 yield of around 48%. Repeating the separation using real agricultural biogas yielded almost the same results, with the additional confirmation that H2S is effectively separated into the permeate, meaning the resulting retentate is significantly desulfurized. Single-stage separation was further expanded with experiments utilizing 2 parallel modules. Similarly in this case, the required quality of the retentate > 95 vol. % was achieved, with slightly increased methane yield of 50%. In the case of two-stage separation proper pressure balancing between 1st and 2nf stage likely did not occur, as the CH4 content in the retentates R1 and R2 had a rather parabolic trend. By the end of the experiment, the CH4 content in the mixed retentate continued to increase, but did not exceed 80 vol. %. Thus, this configuration did not meet the quality requirements for biomethane, although the methane yield increased to 86%. Simple computational models for single-stage and more complex module configurations were assembled in MS Excel based on the volumetric balances of laboratory experiments.