[ Renewables ] higher than that of carbon dioxide , capturing methane and burning it to produce carbon dioxide is much better for the environment . The biogas generated in the digester is collected through a network of pipes and transferred to a gas storage system , where it remains until it is ready for use or further processing . Biogas serves various purposes : it can be directly used as heating or cooking fuel or channeled into a combined heat and power ( CHP ) generator to produce heat and electricity . This flexibility makes biogas a valuable local energy source , suitable for households , farms , communities , and industries . Biogas or generated electricity can also be fed into the grid to contribute to the broader energy supply . Additionally , biogas can be further processed , resulting in a higherquality fuel suitable for converted road vehicles . This upgraded biogas , known as renewable natural gas ( RNG ) or biomethane , has a similar quality as fossil-based natural gas , typically containing 90 % or more methane . The material left over after digestion , called digestate , accounts for around 50 % of the input mass . Digestate is a valuable fertilizer that significantly reduces greenhouse gas and odor emissions compared to unprocessed manure fertilizer . Rich in nutrients , digestate can be applied as a liquid or a solid , thus diminishing reliance on costly and potentially harmful chemical fertilizers .
[ Renewables ] higher than that of carbon dioxide , capturing methane and burning it to produce carbon dioxide is much better for the environment . The biogas generated in the digester is collected through a network of pipes and transferred to a gas storage system , where it remains until it is ready for use or further processing . Biogas serves various purposes : it can be directly used as heating or cooking fuel or channeled into a combined heat and power ( CHP ) generator to produce heat and electricity . This flexibility makes biogas a valuable local energy source , suitable for households , farms , communities , and industries . Biogas or generated electricity can also be fed into the grid to contribute to the broader energy supply . Additionally , biogas can be further processed , resulting in a higherquality fuel suitable for converted road vehicles . This upgraded biogas , known as renewable natural gas ( RNG ) or biomethane , has a similar quality as fossil-based natural gas , typically containing 90 % or more methane . The material left over after digestion , called digestate , accounts for around 50 % of the input mass . Digestate is a valuable fertilizer that significantly reduces greenhouse gas and odor emissions compared to unprocessed manure fertilizer . Rich in nutrients , digestate can be applied as a liquid or a solid , thus diminishing reliance on costly and potentially harmful chemical fertilizers .
Better than concrete Concrete , and to a lesser extent , carbon steel are currently the most common digester tank materials , mainly because of their lower initial cost . However , concrete tank construction must be relatively large scale to be cost effective , requires heavy machinery , is labor intensive and takes a long time to cure . Regular maintenance is crucial to prevent leakages in a digester . Leaking gas , water and odor can cause serious problems for the plant and its surrounding areas . Nevertheless , corrosion is difficult to avoid in concrete and carbon steel digester tanks , even when a special coating system is utilized . Stainless steel tanks , on the other hand , can be quickly installed without the need for heavy machinery , scaffolding or cranage . Typically circular in shape , with diameters up to 35 m , these tanks are assembled on-site by bolting segments of stainless steel sheet together . The tanks are built up ring by ring , starting with the top ring . The partially built tank is then lifted with simple jacks to make space for assembly of the next ring , until the desired height is reached . Prefabrication and construction allow for a precise fit and individual design of the tanks . Due to the segmental design of the tanks , vertical extensions can easily be added at a later stage . Even after years of use , the tanks can be dismantled and reconstructed at a different location . At the end of its long life , stainless steel can be sold as valuable scrap which is 100 % recyclable .
Avoiding corrosion Corrosive compounds , such as organic acids , hydrogen sulfide or chlorides are unavoidable byproducts of the biogas production process . The type and concentration of these byproducts
depend on the composition of the feedstock and the operating conditions inside the digester . Unprocessed plantbased feedstock generally results in the least corrosive byproducts . However , if the feedstock contains residues from meat or fish processing , higher levels of sulfur compounds may be produced . Similarly , if the feedstock includes convenience food or food scraps , sodium chlorides may be present , contributing to the corrosivity . The desulfurization of biogas , which is necessary before feeding it into a CHP generator , can also produce highly corrosive byproducts . Managing the corrosive compounds in biogas production is crucial to prevent damage to the equipment . Repairing and restarting a digester is a complex and time-consuming process , so using materials that resist corrosion in the first place is key . Fortunately , there is a wide range of stainless steel grades available
Japan is the most earthquake-prone country on earth . While it remains heavily dependent on fossil fuels , renewable energy already accounts for one-fifth of total energy production . Stainless steel biogas tanks are resilient and can easily
Photo © Weltec Biopower be customized to meet earthquake-resistance requirements as well as local wind load specifications . This new plant in Saitama near Tokyo converts 12,000 tonnes of organic waste , including cattle manure from a nearby farm , into energy each year . Three stainless steel tanks for upstream feedstock storage , digestion and digestate storage ensure an efficient and durable production process of the biogas plant .
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