How to harness greenhouse gas emissions?

In an increasingly approaching future, greenhouse gas emissions (GHGs) being effectively utilised as resources in the generation of high-value materials or products is becoming more of a reality. The valorisation of these gas streams has been gaining momentum for years as part of sustainable biological processes, thus providing an alternative to traditional technologies for their elimination. These are known as GHG biorefineries. Let’s discuss the types of biorefineries, the bioproducts that can be obtained through them, and an example of a biorefinery we are currently working on.

In this context, GHG biorefineries (spanish) emerge as integrated structures where biotechnological processes take place to transform these gases into biomass associated with high-value bioproducts of interest in the market, through the use of microorganisms. Over the past decades, these biological treatments have positioned themselves as promising technologies, not only for their efficiency but also for their ease of integration into circular economy models. The microorganisms employed in these systems are mostly capable of operating at ambient pressure and temperature, thereby requiring less energy compared to physical-chemical treatments for GHG elimination.

However, the challenge of these technologies lies in deepening the understanding of the microbiology of these processes and in developing systems that maximise gas transfer to ensure high yields at a large scale.

High-value bioproducts that can be obtained in these biorefineries

The development of C1 gas bioconversion biotechnologies has advanced notably in recent years, as it is relatively straightforward to create added value through the direct bioconversion of methane (CH4) or CO2 streams into certain bioproducts, in industries such as food and beverage, waste management plants, or biogas or bioethanol plants.

Some of the bioproducts that have been extensively studied regarding CH4 biorefineries are:

• Biopolymers or polyhydroxyalkanoates (PHAs) are one of the most studied options for CH4 valorisation, primarily because they offer a more sustainable alternative to conventional petrochemical analogues such as polyethylene and polypropylene.
• Ectoine, a cyclic imino acid that effectively stabilises enzymes, nucleic acids, and DNA-protein complexes, is commercially a high-value bioproduct for the pharmaceutical industry, with cosmetics being its main area of application.
• Antibacterial compounds produced by some methanotrophic cultures (such as Methylocystis minimus and Methylobacter luteus) have high potential in combating antibiotic resistance.
• Single-cell protein (SCP), also known as microbial unicellular protein, leads an extensive field of research in both industrial and academic settings. It is one of the most advanced products within methane biorefineries and is widely accepted in the aquaculture, mariculture, and animal feed markets. Commercial products produced with methanotrophs, such as FeedKind™ (Calysta, USA) and Uniprotein™ (Unibio A/S, Denmark), are approved by the EU (Directive 95/33/EC) for use in protein feeds for salmon and livestock.

Figure 2: Uniprotein® Protein-Rich Biomass. Source: Unibio.

Alternatives to reduce dependence on petroleum and fossil gas for chemical production

Regarding CO2 biorefineries, there are numerous technologies for its capture and utilisation (CCU). In addition to the widely known ones, which produce biofuels as final products, CCU processes using CO2 as a raw material provide another alternative to reduce dependence on petroleum and fossil gas for chemical production and other materials. Some examples of these applications include:

• Biofuel production: The case of methanol production from CO2 has been extensively developed, reaching levels such as the Carbon Recycling International plant. This plant has been developed in a project aiming to achieve an annual production capacity of 110,000 tonnes (330 tonnes per day).
• Different biopolymers have been produced from CCU technologies. An interesting example is the German company Covestro, which, after achieving textile fibres and mattress foams, reported in 2021 the successful production of surfactants from CO2 with good washing properties and biodegradability.
• Obtaining organic acids is also noteworthy, such as formic acid through electrochemical conversion or succinic acid through bacterial fermentation. These types of bioproduction, culminating in compounds of interest for the chemical industry, fall under Gas2Chemicals technologies.

Figure 3: CO2 Bioconversion Scheme. Source: CO2Value.

Gas2Chemicals: NEOSUCCESS

The NEOSUCCESS project, part of the European Union’s H2020 Innovation and Development programme, focuses on scaling up and introducing to the market a containerised industrial unit capable of simultaneously carrying out biogas purification to biomethane and second-generation biosuccinic acid production processes (spanish).

AINIA, as a subcontracted entity by IVEM and NORVENTO, acts as a strategic innovation partner, supporting technical and commercialisation tasks of the technology.

The technology underpinning this ambitious project is based on the use of a bacterial strain with the ability to capture CO2 from the biogas stream, thus purifying it into biomethane, and metabolising sugars present in sugary waste through fermentation to a mixture of acids, including biosuccinic acid.

Despite a delayed start due to the COVID-19 pandemic, the NEOSUCCESS project continues to achieve milestones in its second year. During 2022, the project’s partner universities, DTU and AUTH, have accelerated their technology research through laboratory tests and optimizations focused on attempting to obtain an improved bacterial strain that will allow for higher rates of biomethane and biosuccinic acid. Additionally, the design and process parameters were adjusted, a key element for the subsequent piloting of the industrial subunit at the Paterna WWTP (Valencia).

Furthermore, the engineering companies within the consortium, IVEM and NORVENTO, have completed the commissioning of the UpStream (USP) and DownStream (DSP) (spanish). After installing the DSP subunit in the first quarter of 2022, the first tests were conducted with the sugary residue provided by a confectionery factory. Following these tests, it is expected that the remaining trials will provide figures that consolidate this technology as a powerful tool for the circular economy.

SDGs in GHG biorefineries

With gas bioconversion technologies, a cornerstone of these biorefineries, contributions are made to SDGs such as 7 (Affordable and Clean Energy), 9 (Industry, Innovation, and Infrastructure), 11 (Sustainable Cities and Communities), and 13 (Climate Action), among others.