Bioenergy
Pipelaying for district heating in Le Mans , France . Photo : James Chater .
How district heating works : ( 1 ) Waste is combusted to heat water , which ( 2 ) is circulated in the district via insulated pipes ( with inner lining made from stainless steel ); ( 3 ) in each building a substation receives the hot water , which then passes to a heat exchanger . ( 4 ) A secondary circuit inside each building distributes heating and hot water to each residence within the building . Photo : James Chater , from a poster announcing a project in Le Mans , northern France .
Pros and cons
The main argument in favour of bioenergy is that it decarbonises the production of energy by relying on feedstock that is self-renewing : the CO2 absorbed by plants as they grow offsets some of the CO2 emitted during the manufacture process . ( In addition , Bioenergy Carbon Capture and Storage – BECCS – can be applied .) The case for biofuels is especially powerful for heavy-duty transport systems where the prospects of electrification are limited : jet aircraft , large ships , HGVs , heavy industry ( Outokumpu , for example , is building a pelletising plant that will allow it to replace fossil coke with biomass in its stainless-steel production ). A third advantage of bioenergy is the opportunity to cut waste and advance the circular economy . Waste-to-energy ( WtE ) in combination with district heating is an example of how to kill two birds with one stone : disposing of waste that would otherwise have to be incinerated or sent to landfills ( a major source of methane emissions ) while heating homes at lower cost and with fewer emissions . Other benefits include enhanced energy security and a boost to local economies . Apart from anaerobic digestion , other processes used in WtE include incineration / combustion , which produces heat for district heating or electricity ; gasification , which involves heating in a controlled , oxygen-limited environment to produce syngas ; and pyrolysis , where biomass is heated to high temperatures in an oxygen-free environment to produce gas for energy or solid and liquid materials that can be refined as bio-oil and chars . Critics of bioenergy point to the high costs and dependence on subsidies ( does bioenergy make sense when the costs of wind and solar have been plummeting ?), competition with recycling ( diversion of waste that could otherwise be recycled ), technological challenges ( many processes have been implemented only recently ) and the “ food versus fuel ” argument , which maintains that biofuels take up land that could be used to grow food ( an objection that applies more to first-generation than later biofuels ).
Valves
In biomass treatment processes , various types of valves can be used depending on the specific application and requirements . Valve selection depends on factors such as the type of biomass being treated , operating conditions , pressure and temperature requirements and the desired flow control characteristics . In anaerobic digestion , micro-organisms break down biodegradable material in environments without oxygen . The process is used for waste management and fuel production ; anaerobic digestion gate valves are used in this process . Another type of valve found in a biogas plant is the ‘ slam shut ’ isolation valve . Here , butterfly valves can be most useful .
Verbio ’ s Nevada biomethane plant , using maize as feedstock , went online in 2021 .
References ( 1 ) https :// www . iea . org / energy-system / renewables / bioenergy .
( 2 ) https :// hempking . eu / en / hemp-fuelwhat-is-it ; https :// www . sciencedirect . com / science / article / abs / pii / S1364032121000794 ).
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