SMART: Strategies of Methane. Anaerobic digestion and sustainable usage of lignocellulose biomass and digestate
| Project Team: | Marko Blagojevič, Gašper Rak, Blaž Stres |
| Duration: | 24 Months 1.10.2024-30.9.2026 |
| Project Code: | V4-24026 |
| Lead Partner: | University of Ljubljana, Faculty of Civil and Geodetic Engineering |
| Project Leader: | Sabina Kolbl Repinc |
| Other project Partner’s Organization: | Kemijski inštitut |
| Source of Finance: |  ARIS, MOPE  |
| Key words: | lignocellulosic material, biogas, methane, methane potential, anaerobic digestion, optimisation, pre-treatment, digestate, environmental impacts,further use of digestate |
Description:
The project and work programme focus on testing the methane yield of lignocellulosic materials for biogas production on a laboratory scale model.Biogas production by anaerobic digestion represents a flexible and sustainable renewable energy source. Anaerobic digestion is a biochemicalprocess in which micro-organisms break down organically degradable substances in the absence of oxygen, producing biogas, which consistsmainly of carbon dioxide (CO2) and methane (CH4). Efficient anaerobic digestion of lignocellulosic substrates such as wood requires a nitrogen-richrhizoblast to optimise the carbon/nitrogen (C/N) ratio, which should be between 15 and 30. Anaerobic digestion must be carefully monitored andoptimal conditions such as temperature, pH, organic load, hydraulic residence time and volatile fatty acid content must be maintained.Lignocellulose, the main component of woody biomass, is composed of cellulose, hemicellulose and lignin. Cellulose and hemicellulose can bedegraded anaerobically, while lignin requires oxygen for its degradation. This requires pre-treatments of lignocellulosic substrates involving physical,chemical and biological methods. Various pre-treatments can improve lignocellulose degradation and thus increase methane production, but thetranslation of laboratory results to an industrial scale is challenging. The use of real inoculum and adaptation to real conditions in biogas plants isnecessary. Optimisation of biogas production can also be done by codigestion of different substrates for which mathematical models are used todetermine the optimal mixtures. The wood industry produces large quantities of woody biomass that could serve as feedstock for biogasproduction. The exploitation of digestate as an important source of raw materials in the circular economy allows the use of beneficial substances such asnitrogen, phosphorus, potassium and micronutrients as an alternative to synthetic fertilisers, which helps to improve the physical properties of soils,reduce the need for chemical fertilisers and greenhouse gas emissions, while opening up potentials for energy production, composting, theproduction of bioplastics and building materials, and the extraction of lignins and other aromatics for further use. In addition, we will identifypotential negative environmental impacts and make proposals to reduce them, allowing digestate to be used sustainably and safely in a variety ofapplications.
Main Goals:
The research project aims to investigate the potential of using lignocellulosic materials for biogas production under laboratory conditions in Slovenia. Organic and anaerobically degradable substrates are suitable for anaerobic digestion and subsequent biogas production. One of the main challenges in biogas production from lignocellulosic materials is their high variability in quantity and chemical composition. Different types of wood, crop residues and other lignocellulosic sources have different chemistries and physical properties, and have different seasonal distributions throughout the year, which have a significant impact on the efficiency of anaerobic digestion over time. As a consequence, biogas production may be lower than the realistically achievable, i.e. on an industrial scale, potential, while at the same time there are temporally distributed but different inhibitory effects of each substrate when it is reintroduced, leading to acidification and unpleasant odours, a decrease in process efficiency due to the formation of inhibitory aromatic compounds from lignin, prolonged hydraulic residence times, a decrease in the consumption of substrates per unit of time. Therefore, the first objective of this project is to determine the biomethane potentials of different lignocellulosic materials in the laboratory, in order to provide better insight into the anaerobic degradation of lignocellulosic materials and the kinetics and quantity of methane production. The compilation of these data in the form of new entries in the Methane Database (http://methane.fe.uni-lj.si/) will be followed by the optimisation of biogas and methane production from woody biomass with different pre-treatments, a limited number of combinations of complementary co-constituents, and modelling. The approach will provide for optimisation based on mixture design using a mathematical model. This model will allow us to obtain the optimum ratio of woody biomass to nitrogen- and micronutrient-rich substrates. For the purpose of the calculation, we will measure the methane potentials of different mixtures containing different proportions of woody biomass and predict the optimal combination for maximum methane production, which can also be experimentally verified to validate the model. This will take into account the physicochemical properties of the individual substrates. On the basis of the results obtained at the laboratory scale, we will provide a plan for transferring the results obtained at laboratory conditions to a larger scale model. On the basis of the results obtained at the laboratory model scale, we will provide a plan for transferring the results obtained at laboratory conditions to a larger model scale. The starting point will be the methodology of our successful previous studies on realistic particle sizes of both inoculum and substrate, and realistic mixing ratios, which will allow us to bring the measurements closer to more realistic values of methane yields that are applicable to real biogas plants. Digestate is a by-product of the anaerobic degradation of lignocellulosic substrates, which include woody biomass, crop residues, agricultural wastes and other organic materials rich in cellulose, hemicellulose and lignin. The use of digestate is key to the circular economy as it allows the reuse of nutrients and organic matter in agriculture. However, digestate from lignocellulosic substrates requires special treatment because of its specific composition and properties. Therefore, the aim of this research project is to investigate the possibilities for further use of digestate. This will include the examination of the potential of digestate as (i) a fertiliser for agricultural land; (ii) an additive to composting; (iii) an additive to improve the properties of biocomposites using lignocellulosic fibres; (iv) a source of a complex mixture rich in lignins and aromatic compounds suitable for extraction by biodegradable and cyclically applicable solv
Work Packages:
WORK Package 1: Review relevant national and international literature and measure the biomethane potential of lignocellulosic biomass at laboratory scale and transfer to a larger scale. WP1 will include a review of relevant domestic and international scientific and technical literature in the field of the proposed project. We will use our experience of working on a real biogas plant as a starting point, as well as the literature mentioned under point 15 and the references listed in these boxes. We will build on the literature review and apply the experience, knowledge and best practices gained in laboratory experiments where we will perform measurements of the biomethane potentials of lignocellulosic substrates and pre-treated substrates.
WORK Package 2 (WP1S1): Determination of the optimum degradation conditions of woody biomass for biogas production Task 2.1 (WP2.1): Review of relevant national and international literature on the optimisation of biogas and anaerobic digestion production We will review PubMed data, use recent tools for machine condensation of information (ChatGPT), check publicly available patent office records, EU Commission guidelines, Scandinavian and German interest groups.
WORK Package3: Composites WP3 will carry out a review of relevant domestic and foreign scientific and technical literature in the field of the proposed project. The use of lignocellulosic digestate from biogas plants has many potential benefits and applications, especially in the fields of agriculture, circular economy and environmental management. Digestate, which is a by-product of anaerobic digestion in biogas production, is rich in organic matter and nutrients that are useful for plant growth, as well as fibres of industrial interest and chemical compounds that can be extracted and used for further modification (lignin and other aromatic derivatives for further chemical modification) using new techniques.
WORK Package 4 (WP4): Identification of potential negative environmental impacts with proposals for their reduction.