Biogas from bagasse: An alternative to conventional combustion

Biogas plants primarily produce biogas from organic matter. This is accomplished through anaerobic digestion, a process in which bacteria break down organic matter in the absence of oxygen. The amount of biogas produced and the substrates used are critical success factors for biogas plants.

Plant residues from the industrial processing of sugarcane, such as lignin-containing plant fibers like bagasse, are a potentially lucrative substrate for biogas production.

Bagasse is rich in cellulose and hemicellulose, which are easily digestible by anaerobic bacteria, and has a high dry substrate content, making it an attractive option for biogas production. In addition to generating thermal energy and electrical power for sugar production, using sugarcane plant residues for biogas production can provide a sustainable source of energy and reduce greenhouse gas emissions from waste disposal.

Could bagasse be effectively fermented into biogas using anaerobic digestion? Could this offer an alternative to combustion, which emits CO2 and particulate matter?

Yes, bagasse can be effectively fermented into biogas using anaerobic digestion. This offers an alternative to combustion, which emits par- ticulate matter. The potential analysis in the laboratory, as described in Figure 001_Fermentation_test_Bagassere_ Syrup, shows that bagasse can be effectively fermented to produce biogas. The yield of biogas from bagasse was tested in comparison to sugar syrup using a continuous fermentation test based on Standard 4630 of the Association of German Engineers (VDI), Fermentation of Organic Substances—Substrate Characterisation, Sampling, Material Data Collection, and Fermentation Tests.

We have performed a laboratory fermentation test where we used a mixture of 4.5 litres of fermented material from renewable resources and ten grams of organic solid matter from bagasse in a 6-litre fermentation container. The mixture was then fermented for 45 days at a temperature of 39 degrees Celsius.

The test results show that the fermentation process leveled off at an average of 180 Nl/kg oDM (organic dry matter) after growing exponentially for 12 days at 39 degrees Celsius. One tonne of bagasse with 45.5% oDM content yields 85.5 Nm3 of biogas, which can be considerably increased if the material is shredded before fermentation. Therefore, bagasse can be a viable feedstock for anaerobic digestion, and the resulting biogas can be used as a renewable energy source with lower green house gas emissions than traditional combustion methods.

The lab tests show that the amount of biogas that can be made from bagasse is comparable to the amount that can be made from good cattle manure. Both can make a lot of biogas when they are put through anaerobic digestion. Additionally, the use of fermentation residues as organic fertilizers for agricultural land has several benefits, such as improving the water-binding capacity of the soil, contributing to the bioactivity of the soil, and reducing the need for mineral fertilizers.

Furthermore, biogas production from bagasse can be a more sustainable and envi- ronmentally friendly alternative to combustion, as it can substitute the emission of greenhouse gases. The savings from reduced greenhouse gas emissions can be traded in the form of CO2 certificates in the EU and in countries like India with the cap-and-trade system. This can provide an additional economic incentive for the implementation of biogas plants using bagasse as a substrate. Overall, the use of biogas plants for energy production offers several advantages over combustion, including reducing greenhouse gas emissions, producing organic fertilizers, and earning CO2 certificates through emissions trading.

According to the results of Figure the fermentation test, around 180 kWh of electricity can be generated per tonne of bagasse. Furthermore, the methane content in the biogas produced from bagasse is approximately 50%, which can be processed into biomethane too. Given that one tonne of sugar cane yields approximately 280 kilograms of ba- gasse, this byproduct could be a valuable resource for biogas plants. There is significant potential for utilizing ba- gasse as a substrate for biogas production in India, where sugar cane cultivation is significant, with a volume of 355 million tonnes per year as of 2020-2021.

Bagasse is utilised solely for its thermal properties between 150 and 270 days per year, during the harvesting and production phases of sugarcane production. Biogas plants, on the other hand, can be supplied with organic substrates all year. Bagasse stored in silos is an excellent choice for this application. because it has the potential to supply the plant with substrate for an entire year.

But, in addition to agricultural, industrial, and administrative waste, various types of organic residues can be employed as substrates for fermentation. The flexible biogas has the potential to be directly turned into electricity and heat, both of which can then be sold on the energy market. Alternatively, it can be purified and processed using PSA or membrane technologies in order to concentrate the biogas into biomethane. This would accomplish the same goal. It serves both as a storage medium and a feedstock for the production of bio-CNG or green hydrogen, which in turn contributes to a reduction in the amount of carbon dioxide that is released into the atmosphere.