The possibilities of balancing gas supply and demand with a green gas supply chain were analyzed. The considered supply chain is based on co-digestion of cow manure and maize, the produced biogas is upgraded to (Dutch) natural gas standards. The applicability of modeling yearly gas demand data in a geographical region by Fourier analysis was investigated. For a sine shape gas demand, three scenarios were further investigated: varying biogas production in time, adding gas storage to a supply chain, and adding a second digester to the supply chain which is assumed to be switched off during the summer months. A regional gas demand modeled by a sine function is reasonable for household type of users as well as for business areas, or a mixture of those. Of the considered scenarios, gas storage is by far the most expensive. When gas demand has to be met by a green gas supply chain, flexible biogas production is an interesting option. Further research in this direction might open interesting pathways to sustainable gas supply chains.
In order to gain a more mature share in the future energy supply, green gas supply chains face some interesting challenges. In this thesis green gas supply chains, based on codigestion of cow manure and maize, are considered. The produced biogas is upgraded to natural gas quality and injected into the existing distribution gas grid and thus replacing natural gas. Literature research showed that relatively much attention has been paid up to now to elements of such supply chains. Research into digestion technology, agricultural aspects of (energy) crops and logistics of biomass are examples of this. This knowledge is indispensable, but how this knowledge should be combined to help understand how future green gas systems may look like, remains a white spot in the current knowledge. This thesis is an effort to fill this gap. A practical but sound way of modeling green gassupply chains was developed, taking costs and sustainability criteria into account. The way such supply chains can deal with season dependent gas demand was also investigated. This research was further expanded into a geographical model to simulate several degrees of natural gas replacement by green gas. Finally, ways to optimize green gas supply chains in terms of energy efficiency and greenhouse gas reduction were explored.
The production of biogas through anaerobic digestion is one of the technological solutions to convert biomass into a readily usable fuel. Biogas can replace natural gas, if the biogas is upgraded to green gas. To contribute to the EU-target to reduce Green House Gases emissions, the installed biogas production capacity and the amount of farm-based biomass, as a feedstock, has to be increased. A model was developed to describe a green gas production chain that consists of several digesters connected by a biogas grid to anupgrading and injection facility. The model calculates costs and energy use for 1 m3 of green gas. The number of digesters in the chain can be varied to find results for different configurations. Results are presented for a chain with decentralized production of biogas, i.e. a configuration with several digesters, and a centralized green gas production chain using a single digester. The model showed that no energy advantage per produced m3 green gas can be created using a biogas grid and decentralized digesters instead of one large-scale digester. Production costs using a centralized digester are lower, in the range of5 Vct to 13 Vct per m3, than in a configuration of decentralized digesters. The model calculations also showed the financial benefit for an operator of a small-scale digester wishing to produce green gas in the cooperation with nearby other producers. E.g. subsidies and legislation based on environmental arguments could encourage the use of decentralized digesters in a biogas grid.
By transitioning from a fossil-based economy to a circular and bio-based economy, the industry has an opportunity to reduce its overall CO2 emission. Necessary conditions for effective and significant reductions of CO2-emissions are that effective processing routes are developed that make the available carbon in the renewable sources accessible at an acceptable price and in process chains that produce valuable products that may replace fossil based products. To match the growing industrial carbon demand with sufficient carbon sources, all available circular, and renewable feedstock sources must be considered. A major challenge for greening chemistry is to find suitable sustainable carbon that is not fossil (petroleum, natural gas, coal), but also does not compete with the food or feed demand. Therefore, in this proposal, we omit the use of first generation substrates such as sugary crops (sugar beets), or starch-containing biomasses (maize, cereals).
At gas stations, tetrahydrothiophene (THT) is added to odorless biogas (and natural gas) for quick leak detection through its distinctive smell. However, for low bio and natural gas velocities, evaporation is not complete and the odorization process is compromised, causing odor fluctuations and undesired liquid accumulation on the pipeline. Inefficient odorization not only endangers the safety and well-being of gas users, but also increases gas distribution companies OPEX. To enhance THT evaporation during low bio and natural gas flow, an alternative approach involves improve the currently used atomization process. Electrohydrodynamic Atomization (EHDA), also known as Electrospray (ES), is a technology that uses strong electric fields to create nano and micro droplets with a narrow size distribution. This relatively new atomization technology can improve the odorization process as it can manipulate droplet sizes according to the natural and bio gas flow. BiomEHD aims to develop, manufacture, and test an EHDA odorization system for applying THT in biogas odorization.
The Cashing Cashew project focuses on isolation and purification of Cashew Nut Shell Liquid (CNSL) from Cashew Nut Shells (CNS) in order to fully utilize this valuable by-product of the cashew nut production. Global cashew nut production is about 4 million mt/ tons/yr. Of the cashew nut, about 70 % is shell that is removed in processing and currently typically burned as a dirty and inefficient fuel or discarded as waste. This is not only creating an environmental issue but also wasting valuable by-products. The shell contains circa 20-30 % brown viscous liquid, Cashew Nut Shell Liquid (CNSL). This natural resin contains valuable chemical components, for example, cardanol, cardol, and anacardic acid. CNSL and its derivatives have several industrial uses as for example biobased additives, polymeric building blocks, and biodiesel. Part of the CNSL can be extracted during the roasting process prior to separating the shell and nut kernel. The shell waste still has a high CNSL concentration that can be isolated by solvents or pressing (expeller). Expeller process is simple and not capital-intensive; therefore it is commonly used. The main disadvantages of the method are the high energy consumption and that 3-5 % oil remains in the press-cake producing harmful gases in burning. Also, the resulting cake is too dense to be further processed to charcoal or other useful application. The objective of this project is to study the purification of the CNSL obtained from pyrolytic isolation to find the most efficient way of making use of the CNSL oil and the total Cashew Nut Shell biomass. An initial evaluation of potential applications is also performed.
