Anaerobic fermentation of spring fresh wild plants

Abstract

Noticeable climate change around the world has led to the search for more and more low-carbon technologies. Biogas is also produced in Latvia and is used to produce electricity and heat. The use of biomethane in transport needs to be further developed to replace diesel and petrol engines more quickly. In the spring, biogas producers sometimes have difficulty securing good quality raw materials. The raw materials procured in the previous year are not always left in sufficient quantities. It happens that long-term storage of raw materials also breaks down. The amount of manure, which is mainly used by Latvian biogas plants, cannot usually be increased. There is a shortage of raw materials and gas yields are falling. Biomethane yields can be increased by substances that catalyze the anaerobic fermentation process. They can also be found in spring plants. The use of spring plants such as dandelions (taraxacum), which grow over large areas, could improve the situation. The methane potential of dandelions and three other plants was investigated in this study. Plants such as celandine (Chelidonium majus), European twist (Cuscuta europaea) and elderberry (Sambucus nigra) have specific effects. Elderberry and celandine have a healing effect, but the European twist is a parasitic plant. Therefore, it seemed interesting to find out whether these plants will somehow specifically affect the activity of bacteria in the process of anaerobic fermentation. Fourteen bioreactors were filled with fresh plants collected in the field and in the garden on the same day. The two bioreactors were filled with inoculum only. Anaerobic fermentation took place at 38C and lasted from 10.05 to 7.06. The methane potential was 0.486 L·gDOM for dandelions, 0.440 L·gDOM for elderberry leaves, 0.488 L·gDOM for European twist and 0.403 L·gDOM for celandine. All the plants tested are very useful as feedstocks for methane production in anaerobic fermentation. However, expectations that Sambucus nigra, Chelidonium majus and Cuscuta europaea will show some catalytic properties for anaerobic fermentation were not met.