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SENSORS, TRANSDUCERS & TRANSMITTERS
Antti Heikkilä, Industry Expert and Product Manager at Vaisala, discusses the role of the latest monitoring technology in biogas production
C
ountries around the world are urgently seeking alternatives to fossil fuels in order to lower greenhouse gas (GHG) emissions and thereby limit global warming. One of the ways in which this can be achieved is by replacing natural gas with biomethane, but this can only be a viable solution if it is environmentally and financially sustainable. To achieve this goal, it is necessary to monitor biogas production continuously so that the process can be optimised. Vaisala has therefore developed monitors that are capable of measuring methane, carbon dioxide and humidity in-line.
Formed over a timespan of millions of years when layers of organic matter decompose deep underground at high temperature and pressure, natural gas consists of methane and small amounts of other gaseous hydrocarbons. Natural gas is therefore a fossil fuel, and its combustion is responsible for a significant portion of global greenhouse gas emissions. For example, according to the USEPA, emissions from natural gas consumption represented 79% of the direct fossil fuel CO2 emissions from the (USA) residential and commercial sectors in 2020.
Spiralling energy costs, supply chain disruption and the GHG emissions associated with the extraction, transport, and combustion of natural gas mean that cheaper, reliable, and more sustainable alternatives to natural gas are required. As fossil fuels are phased out during the green transition, it has become necessary to find alternative sources of clean energy through innovation. New technology therefore has a vital role to play as we move into a profitable and sustainable era of green energy.
Replacing natural gas with biomethane
Biogas represents an important green alternative, but only if it is economically viable and able to compete with the alternative forms of renewable energy available. In-line monitoring of biogas production and the upgrading process to biomethane enable production efficiency improvements; making biomethane an economically and environmentally viable alternative to fossil fuels.
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Around 75% of the biogas currently produced in the EU is used as a source of local heat and power generation, with almost 20% of biogas being converted to biomethane. According to the European Commission’s RePowerEU scheme, biomethane production is projected to increase tenfold by 2030 and to grow even more rapidly up to 2050. Today, the production cost of biomethane has been estimated to be around 80 euros/MWh, but the European Biogas Association expects this to fall to 55 euros/MWh in the future. These increases in both production and efficiency can only be achieved using the latest process control instrumentation.
lower or prevent any potential emissions. Biomethane is a useful alternative where a gas fuel must be used, or
where natural gas is used as a feedstock instead of a fuel. In the chemical industry, for example, natural gas is used as an energy source, and as a raw material for the production of ammonia, which in turn is used to produce fertilisers.
Continuous monitoring
Vaisala’s MGP261 and MGP262 both measure methane, carbon dioxide and humidity continuously.
The main difference is that the MGP261 measures 0-100% methane, so applications include various points in anaerobic digestion processes, landfill gas monitoring, activated carbon filter monitoring in biogas treatment processes, and CHP engine feed gas monitoring.
Biogas also offers an opportunity for a more circular economy. This is because the feedstock for anaerobic digestion (AD) can include waste products such as food, crop residues, animal manure, and wastewater sludge, and the digestate from AD can be returned to the land as fertiliser. Biogas represents an attractive opportunity, but its sustainability credentials would be damaged if methane is allowed to slip into the atmosphere from either the AD reactor or the gas upgrading process. This is particularly important because methane is a powerful GHG; roughly 30 times stronger than carbon dioxide, so it is vital that monitoring and process optimisation is employed to
Whereas the MGP262 measures 0-5% methane, so it has been designed for in-situ measurement of the offgas in the biogas upgrading process (concentrating the methane in biogas to natural gas standards), where low concentrations of methane need to be measured reliably and with high accuracy in the presence of high concentrations of carbon dioxide. Substantial infrastructure is in place to facilitate the utilisation of natural gas, so biomethane represents a logical alternative. However, there will be many instances where fossil fuel energy sources can be replaced by other forms of renewable energy such as wind and solar. Biomethane production must therefore be as efficient as possible if it is to compete, and this is where the latest monitoring technology, such as the MGP261 and MGP262, have a vital role to perform.
Vaisala
www.vaisala.com/en
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