AUTOFERM

The increase of greenhouse gas emissions, the environmental degradation and the depletion of fossil fuels naturally direct us to use renewable energy such as biogas. Agricultural applications of anaerobic digestion generate an increasing interest among farmers, energy producers, environmental organizations and government agencies. This process transforms agricultural wastes or bio-wastes (like food industries wastes) in biogas leading to heat and / or electricity or in biofuel. The technical solutions that have to be offered to farmers should be stable, reliable, easy to operate. Biogas is one of the energy mix contributing to the development of renewable energy in France. French agricultural biogas encounters some difficulties for its expansion in our country. Investment is expansive due to the dimensions of the tanks: the difficulty to manage these digestion units leads engineers to take safety margins associated with very long residence times (50-90 days). An increase of the reliability of the agricultural digesters will reduce the residence time and thus will considerably lower the amount of the level of investments. Critical problems occurring in digesters can lead to a break of 2 to 3 months in the digester working plan. The Autoferm program proposes to develop an interactive management tool to survey the biogas production, including early detection of biological and technical problems. Autoferm will involve a lot of selected sensors, tested in the digester environment and a monitoring software providing relevant informations to the operator. This monitoring tool, combined with the development of a predictive model, will become a regulation and control software adapted to biogas plants based on livestock manure. The selection and the testing phase of the sensors are an essential step in the reliability and durability of the final tool. This phase will be carried out on pilot plant in order to find conditions as close as possible to agricultural digesters. For example, sensors such as pH probes in ceramics will be assessed, an infrared sensor of VFA (volatile fatty acids) in the gas phase will be tested (VFA sensors in liquid phase require complex design and are not reliable over time). The first goal of the research step after sensors validation will be to build a monitoring and an alarm tool (algorithm) that can be useful for the farmers. This tool must be able to detect, through the sensors analysis, major troubles occurring in the biogas plant. The Power Bio Company has worked on a digester monitoring software. The selected sensors will feed this monitoring interface in order to have an online evaluation of the biogas plant performances. Monitoring software and supervision tool will be combined to give an accurate information to the farmer. However, due to the complexity of biological reactions in a digester it is necessary to also have a predictive view in order to anticipate possible deviations. The design of a suitable model for the understanding of biological reactions must be able to detect failures to prevent biological disorders within the digester. Phenomenological models based on ADM1 will be adapted to the agricultural biogas plants conditions and will be tested in real conditions. Selected disruptions will be organized in order to test the monitoring system and the effectiveness of model at a pilot scale. Most reliable techniques will be tested on a real farm equipped with a large digester. One of the main perspectives of this work will be the development of an efficient control system ensuring the reliability of agricultural biogas plants and so a help to increase their profitability.