Biomethane, deriving from the purification and upgrading of biogas, is a renewable energy offering big advantages. For the release of this gas into distribution networks, there are strict rules to follow, particularly regarding its odorization
Recent political and economic developments, as well as climate and environmental changes, have led many European countries to implement a common strategy to take full advantage of various forms of renewable energy. Among these, the focus is on biomethane, in particular.
Gas deriving from renewable sources, such as biomethane, can be fed into existing infrastructure and used to support growing energy needs.
In Europe, the target market for biomethane production from agricultural and livestock activities is Germany, where the first plants were started as early as 2007 and are mainly aimed at producing biomethane for feed-in.
Italy, too, thanks to NRRP (National Recovery and Resilience Plan) incentives, is investing in new energy by supporting the production of biogas, biomethane, blends of biomethane / hydrogen and pure hydrogen.
Benefits of biogas and biomethane production
There are many benefits associated with sustainable gases:
- programmable renewable sources;
- reduced reliance on imports;
- development of the local economy;
- environmental sustainability;
- example of circular economy.
In particular, the National Recovery Plan provides incentives for the construction of new sustainable biomethane production facilities (out of organic or agricultural waste) or converted from previous agricultural biogas production.
Biomethane is a renewable and sustainable energy source because it is produced out of nearly inexhaustible biomass that incorporates carbon from the atmosphere in its life cycle. Its consumption thus avoids using fossil carbon fuel deposits, minimizing emissions of climate-changing gases.
In contrast, the production of biomethane deriving from the organic fraction of municipal solid waste (MSW) from sorted collection of waste and agribusiness waste is a classic example of biowaste circular economy. It is a process that transforms waste into high added-value products (compost and biomethane), increasing the sustainability of the entire cycle.
One of the distinctive features of biomethane as a renewable source lies in its use, which can be flexible because it may become a fuel in all kinds of energy uses (transportation, industry, power generation, heating & cooling and cooking), as well as a raw material to produce biomaterials and biochemicals. In addition, because it is fully comparable to natural gas, it is compatible with existing transportation infrastructure and storage facilities.
Difference between biogas and biomethane
What do we mean by biomethane and biogas? Let us get it clear
Biogas
Biogas is a mixture of carbon dioxide and methane produced during the process of anaerobic digestion on various organic substrates. Anaerobic digestion is a biological process that occurs in the absence of oxygen (anaerobiosis) through biochemical reactions due to specific bacteria. The process can be divided into three stages characterized by the action of different groups of anaerobic bacteria:
- Hydrolysis;
- Acidogenesis;
- Acetogenesis and methanogenesis (subdivided into acetoclastic / hydrogenophilic).
Biomethane
Biomethane is a gas that contains mostly methane (CH4) and derives from a renewable source. In fact, biomethane comes from biogas that has undergone a purification process (dehydration, desulfurization, removal of ammonia gas, NH3(g), mercaptans, dust) and upgrading (removal of carbon dioxide, CO2) until its quality is that of natural gas.
At the end of the purification and upgrading process, the resulting biomethane contains about 98 percent CH4 and is chemically very similar to natural gas.
The possible end uses of biomethane are therefore fully equivalent to those of natural gas:
- fueling stations
- co-generation in centralized plants
- domestic users (heating and cooking)
- industrial users.
Therefore, it is obvious that biomethane can be an energetically more flexible, thus more efficient as a tool than biogas.
The gas produced, however, may be fed into the gas network only after appropriate compression and odorization.
Why biomethane must be odorized
Biomethane may contain traces of odor-altering substances.
Indeed, combustible gases for domestic and similar use must have a characteristic odor sufficient for people to detect its presence before it may create dangerous conditions.
That is why biomethane odorization is necessary: so that its presence may be felt when a dangerous amount becomes explosive and toxic.
Therefore, odorization is a key treatment for safety during distribution and end use of the gas.
Odorization process
The odorization process is regulated by UNI 7133:2019 "Odorization of household and similar gas" and UNI/TS 11537:2019 "Feeding biomethane into natural gas transmission and distribution networks."
The UNI/TS 11537:2019 standard applies to biomethane produced to be introduced into the natural gas transmission and distribution network and requires two types of tests.
Firstof all, in order to ensure safety also, the standard requires checkingsome chemical and physical characteristicssuch as Wobbe Index, carbon dioxide content, total sulfur content, ammonia,total sulfur content, ammonia, total chlorine, sulfur from mercaptans, etc.
Next, the gas must comply with the odorability requirement. The tests, prescribed in Attachment G of UNI 7133-2:2019, must be carried out by a qualified laboratory that performs rhino-analytical tests on the biomethane sample.
Through rhino-analysis, the only technique to be used for this specific case, it is possible to determine whether the biomethane can be fed into the network and used or not.
LOD srl is the only private Italian laboratory accredited and specialized to perform these specific tests.
Finally, the importance of the UNI/TR 11722:2018 standard "Guidelines for the preparation of risk analysis for producers of biomethane from biomass" should also be emphasized.
The standard specifies that if it is the first biomethane produced after stabilization of the purification processes and related testing, it is also necessary to perform extended chemical-physical analysis by means of Gas Chromatography to identify the presence of interferents such as terpenes that could mask or modify the added odorants.
As explained in this article (within Geonose blog, the odor monitoring application we created) rhino-analysis may also be used for studies on specific odorants (e.g., without sulfur content) or on specific substances, in order to determine their interference threshold
