(The Gist of Science Reporter) Methanol and DME Economy in India [FEBRUARY-2019]

(The Gist of Science Reporter) Methanol and DME Economy in India

[FEBRUARY-2019]

Methanol and DME Economy in India

Introduction

Globally, production and utilization of methanol have been on the rise due to multiple drivers like availability of cheap raw material like coal and natural gas: securing energy supplies among increasing oil prices; strategic like reduction of oil import bills, and environmental concerns about pollution and climate change.
Use of methanol as a fuel and chemical intermediate provides multiple avenues for its utilisation with rapidly increasing demand for automobile and consumer sectors. Methanol is an efficient fuel due to its high octane number (~100) and emits lesser pollutants like SOx. NQx and Particulate Matter (PM) as compared to gasoline.
Methanol-gasoline blends ranging from M15 to M85 have been adopted in countries like China, and it has been established as a transportation fuel along with other applications.
Methanol can be dehydrated to produce Dimethyl Ether (DME) which can replace diesel and also can be blended with LPG. Other applications of methanol include conversion to chemicals formaldehyde, acetic acid and various olefins like ethylene and propylene.
The initiative by Niti Aayog towards the “Methanol Economy” promises to help our nation in mitigating petroleum import costs and at the same time counter problems associated with global warming due to excess CO2, emissions. India imported 37% of its total primary energy demand in 2015-16, whereas the import dependence of crude oil and natural gas has increased from 73% and 17% in 2005-06 to 81% and 40% in 2015-16 respectively.
The current production process for biomethanol involves gasification of biomass to generate syngas which can be converted to methanol using existing catalyst and conversion technology. However, the technology requires cleaning of gas generated and is viable at large scale.
Due to its relatively high cost biomethanol production is limited as compared to standard methanol Also the challenge in logistic of biomass collection provides the opportunity to develop novel approaches in smaller scale and decentralised production processes that reduce the capital costs of biomethanol plant and benefit the rural communities.

Biogas as Feedstock for Methanol Production

Anaerobic digestion of agro-residues and agro-industrial waste into biogas provides a sustainable source of energy Biogas contains methane (CH4) as the major component (50%
-70%) and is an emerging renewable feedstock for fuels and chemicals. Currently, the total biogas production in India is around 2.07 billion m’/year, Biogas produced by digestion of distillery spent wash, food waste, Municipal Solid Waste (MSW), sugar and oil industries can serve as a major feedstock for production of methanol.
The new biofuel policy of India has also put major thrust on the development of Biogas/Bio-CNG plants across the country. According to the estimates of oil marketing companies, approximately 100-120 million tonnes of biogas (50- 60 million tonnes of Bio-CNG) can be produced from different sources. This provides an investment opportunity of around 5000 biogas plants with a capacity of 50 tonnes/day of biogas assuming 300 days of operation.
Growth in biogas plants can support several applications including methanol along with replacement of imported natural gas for existing applications, Methane can be thermo-chemically converted to methanol using syngas route, but the process requires expensive metal catalysts and operates at high temperatures (200°C-900 °C) and pressures (5-20 MPa), Thermo chemical technologies have a high capital expenditure due to large size of plants and require a methane source that is free of impurities. Moreover, existing technologies for methanol production are inefficient due to multiple steps and by-product generation.
Biogas contains carbon dioxide (30%-50%) and trace impurities such as hydrogen sulphide (0-2000 ppm) and purification processes to enrich methane makes it an expensive feedstock for chemical conversion.
Biological conversion of biogas to methanol is an emerging, attractive approach as it may not require biogas purification and uses ambient conditions, reducing operational costs and energy Demands.

Technology Status

The interest in methanol production is the main driver for research into novel process technologies. However, the current scale of production in the natural gas based methanol plants increases the risks and challenges in the introduction of renewable technology routes. The new biomass based technologies may be better deployed in small-scale plants through savings in feedstock supply chain and consumption in local markets.
Improvements in gasification technology can be applied to both renewable and non-renewable sources of methanol. Conventional gasification such as fixed bed, fluidized bed and entrained flow reactors have been proven for commercial biomass to power applications and can be adapted to produce biomethanol. However, high investment costs, low gas quality and poor efficiencies have limited their application to liquid fuel production.
New developments in gasification technologies are focused on plasma gasification along with exploration of improved process integration and intensification for biomethanol production. Although these approaches are technically feasible they are not yet economically attractive for biomass to methanol conversion.
A fermentation-based technology for methanol production can be developed using methanotrophic bacteria, which possess the ability to convert methane to methanol using methane monooxygenase enzyme. The major advantage of a fermentation-based technology lies in the direct conversion of methane to methanol vis-a-vis indirect conversion by chemical catalysis route. Direct biochemical conversion to biomethanol at ambient temperatures provides several benefits like improvement in overall yield and selectivity of the process. Fermentation based processes also have lesser operating cost and can be economical at smaller scale as compared to a chemical process. From environmental viewpoint, fermentation processes are cleaner as they generate lesser effluent and greenhouse gases.
Ethanol production is the best example of a fermentation-based process with wide-ranging capacity plants operating in a decentralised manner. A sugar-ethanol distillery complex installed with a biomethanation system for treating press mud and distillery spent wash can be retrofitted to produce biomethanol from generated biogas, The other benefit of using methanotrophic bacteria lies in its ability minimal media requiring to grow on lesser process inputs. Methanotrophic organisms have better tolerance to impurities like H2S and do not require the cleaning of biogas as in the case of a chemical catalyst. Some of the methanotrophs are reported to utilize CO2, a characteristic that can be further exploited in the biogas to methanol conversion.
R&D of Biomethanol Production National Status In India, agro-residues and agro-industrial wastes form a major source of bio-resource having the potential for bioenergy. Anaerobically converting them to biogas provides a sustainable energy source as well as simultaneous route to nutrient recycling (nutrient-rich compost) to soil. Some studies have been done on the bioremediation potential of Trichloroethylene (TCE) using methanotrophic organisms. Negligible reports are available on the development of wild type or genetically engineered organisms for conversion of methane to methanol. Also synergistic research areas like development of advanced gas fermentation system for increasing gas to liquid mass transfer rates and life cycle analysis studies of biogas to methanol conversion are lagging in comparison to global status.

R&D of Biomethanol Production International Status

At the global level, both chemical and biotechnological routes of direct methane to methanol conversion are under development. For direct methane to methanol conversion using chemical catalysis, several approaches like catalytic gas phase oxidation, catalytic liquid phase oxidation and mono-halogenated methane have been studied. These approaches had challenges like low conversion yields and expensive catalyst. Globally, no direct conversion based plants have been built till date.
The development of MMOs as standalone biocatalysts for methane to methanol bioconversion has been hindered by their structural complexity and requirement for regeneration of reducing power for the biocatalytic reaction.
A polymeric hydrogel material immobilizing the membrane-bound pMMO has been developed which was embedded in a silicone lattice to construct a flow-through bioreactor for production of methanol up to 600 nmol/mg enzyme.
Genome scale metabolic reconstruction models have been studied in Methylosinus trichosporium. Methylomicrobium buryatense and Methylomicrobium alcaliphilum. The model for M. buryatense 5G(B1) strain incorporated 841 reactions using whole genome predictions and expression data. Such models can be applied to study and predict metabolic parameters for nutrient and genetic variations to devise strategies for enhanced methanol accumulation and engineer cofactor regeneration. R&D Interventions to Bridge Technological Gaps.
In order to develop a commercially viable fermentation process for methanol production, more research is required in the area of bioreactor design to improve gas to liquid mass transfer rates. Gas-based fermentation is fundamentally different and more challenging from ‘traditional’ glucose based fermentation for several reasons including the low solubility of methane in aqueous solution; the need to feed multiple gases at high mass transfer rates; and significant heat loads generated from the metabolism of the high-energy methane substrate.
Significant improvements in the methanotrophic strains would be required to further improve the yield, titer and productivity of methanol. An integrated approach based on modern techniques of genetic engineering, enzyme engineering, reactor design and computational fluid dynamics tools would be useful in designing an efficient biocatalyst and a robust bioprocess for biogas to methanol conversion. Toxicity of methanol is one of the major limiting factors in increasing methanol accumulation by methanotrophic strains. To improve the tolerance of methanotrophs to methanol directed evolution strategies like serial adaptation or chemostat cultivations be employed. Directed evolution strategies can also be applied for overcoming inhibitions from impurities like Hydrogen sulphide present in biogas streams.

Commercialisation Roadmap

Biomass/MSW based biogas plants can create a viable alternative for methanol production in India which will be competitive at the global scale. Addition of methanol production unit will result in significant value addition to the. Biogas plants resulting in higher revenue for the biogas. As compared to current applications of biogas like steam and power generation, or enrichment to BioCNG, Biogas to Biomethanol conversion can provide maximum returns per unit of biogas produced.
Development of indigenous technologies will create a viable alternative for methanol production in India which will be competitive at the global scale. The biomethanol production will result in significant value addition to the biogas plants resulting in higher revenue for the biogas as well as the construction of several decentralised small plants across the nation. Biomass-based biogas plants will help in the creation of rural jobs and additional income for fanners. Several small and medium scale industries will be benefitted by the commercialization of biomethanol technology and will help in improving the rural and national economy.