Technology and Evaluation and Monitoring Innovation and Biogas Plant Control Training

One of the main agricultural industry in Southern part of Thailand is the palm oil industry. The industry produces huge amount of wastewater called “Palm oil mill effluent or POME” which is characterized by high organic content (COD 60-100 g COD/l). POME is currently a main source of biogas produced by anaerobic digestion (AD) process. The biogas (50-65% methane and 35-50% CO₂), in turn, is converted to electricity and thermal energy for industrial uses of feed to the commercial grids. Biogas production from POME help to reduce greenhouse gas by capturing CH4 into CO2 before releasing into the atmosphere, substituting fossil fuel, lowering the energy costs for the industry and nearby communities. Moreover, the industry produces other large amount of organic waste including crude-glycerine waste, decanter cake. This waste is not suitable for biogas production by their own but can co-digest with POME which can increase the amount of biogas up to two-folds compared to POME mono-digestion.

However, AD process, in general, is susceptible to load change, pH, temperature, accumulation of volatile fatty acids (VFAs), NH3, Sulfate, other toxic contaminants. Anaerobic co-digestion, albeit increase biogas yield and reduce environmental problem, further complicates the operation of biogas plant. The plants must take higher risk if the systems become unstable, followed by plant failure which incurs very high cost.

The 4-days workshop was offered to the biogas-plant operators, related engineer and technicians, policy makers as well as renewable-energy consultants. Its main objectives were to improve the technical skills of the targeted audiences by enhancing their basic knowledge and skills to use simple calculations in monitoring the state of biogas plants.  The workshop also introduced two mathematical models as tools for monitoring, evaluation, and control system development, namely: simple Monod and extended AMOCO models. A software platform called BMOC 0.1 (Biogas Modeling, Operation, Monitoring and Control) was developed and used in the workshop. In summary, the activities in the workshop included.

– Fundamental of anaerobic digestion (AD) and co-digestion (AcoD) focused on the role of microbial consortium, mechanisms of AD, AcoD, related biochemical reactions, effect of feedstock composition, organic loading, temperature, pH, accumulation of VFA, CH₄ and H₂S.

– Trouble shooting in biogas plant operation, biogas plant stability.

– Basic calculation for biogas engineers and biogas operators: theoretical COD, biogas and methane yield, energy from biogas combustion from proximate and ultimate analysis.

– Fundamental of biochemical methane potential assay.

– Principle of biogas modeling: Development of Simple Monod model (SMD) and its application in biogas production using POME as a feedstock. Simulation of SMD to predict the effect of organic loading, HRT on the biogas plant performance.

– Development of the extended AMOCO model which is suitable for describing a wide range of AcoD including: BMP data, batch, semi-batch and continuous AcoD processes. Emphasis was on the modeling of the Hybrid-Channel Anaerobic digesters, the most widely used digestion system used in POME-based biogas plants in Southern Thailand.

– Cases in biogas production from various kinds of feedstocks, AcoD, plant stability and failure. The BMOC platform was used to illustrate the cases by simulation.

However, due to the Covid-19 pandemic the factory fieldtrip and physical demonstration was not feasible.

The workshop was highly successful. 30 personals from more than 20 biogas plants, energy related private company, academia and policy makers joined the workshop. Over 25 trainees pass a standard examination and were rewarded certifications. Four biogas plants have planned to do further development on model development, simulation for monitoring, performance evaluation and control system development. The activities are on-going actively.