The invisible gas of the plains; Hydraulic regeneration of the network using biomethane

A country like Denmark supplies nearly 40% of the gas flowing in its transmission network through the processing of animal waste and agricultural waste. This action is part of the European Union's comprehensive energy security document known as "Repower". In this program, it is targeted that by 2030, 35 billion cubic meters of biomethane will enter the gas pipelines of this continent.

Ambassador Arjan; Hamid Khodri; PhD in industrial management

Introduction- In this series of notes, each of which is independent from the other, the author tries to provide a basis for public awareness with a fresh look at the link between development and energy in Iran and the world. The following note is the twelfth issue of this series.

Every winter, in order to provide maximum domestic gas, the feed flow of petrochemicals, steel furnaces and some industries faces restrictions. On the other side of the story, the estimation of data from Satba's biomass potential measurement atlas and the analytical reports of Majles Research Center show that more than three hundred thousand tons of perishable livestock, agricultural and urban biomass are produced daily in the country. A significant part of this wealth is produced and released in the same provinces that suffer from pressure drop.

Studies show that the release of this amount of organic matter produces more than three billion cubic meters of volatile methane annually with a climate warming factor 28 times that of carbon dioxide, which is released into the atmosphere at the same time as it pollutes underground water sources.

This duality between stopping or restricting industries due to the limitation of feed supply on the one hand and the waste of methane resources left in the plains on the other hand, indicates the necessity of reviewing the architecture of the country's macro energy structure for a future without gas or with its limitations.

Recent developments in global gas markets show that gas extraction is no longer limited to exploration in the depths of the earth. The number of active units injecting biomethane into gas pipelines in Europe has exceeded 1,600 production centers.

However, the development of this technology is not possible without considering the technical and economic challenges. Critics always point to some key issues, such as the financial burden caused by the collection and transportation of scattered waste, the seasonal fluctuations of agricultural waste production throughout the year, and the risk of possible methane leakage in anaerobic digestion units.

The engineering answer to these concerns lies in the optimal design of the scale. The construction of biomethane units should not be based on small and scattered waste, but should be concentrated in concentrated centers such as livestock megafarms, large sewage treatment plants, and agricultural and industrial complexes.

Also, the issue of seasonality of agricultural residues can be controlled through a more storage process (siloing) and the adoption of a "co-digestion" strategy with continuous sludge and animal manure. Regarding the risk of methane leakage, the risks arising from it can be controlled by using strict safety engineering standards and establishing monitoring systems.

The fundamental difference between raw biogas and biomethane injected into the grid lies in process engineering and thermodynamic indicators. Raw biogas, which is produced from the decomposition of organic waste, is only used for burners, steam boilers, and engines for the simultaneous production of electricity and heat, due to the low purity of methane and the presence of moisture and corrosive compounds. But in advanced refining units, with the use of separator membranes and surface absorption systems, the purity of methane reaches more than 97% and this gas can be used industrially. Of course, by performing cost-benefit calculations, it is conceivable to use both types of this energy in the country's industries.

Domestic experiences in anaerobic digestion (such as the 7.2 MW unit of Firouzbehram Refinery) have been limited to electricity production, and the void of injecting biomethane into the gas network or its industrial application is felt.

The fundamental importance of this approach is revealed when we draw the gas transmission map of the country at the intersection with the poles of agriculture, animal husbandry and food industries. Gas transmission arteries mainly extend from the southern fields to the northern provinces, and after traveling long distances, they face a severe pressure drop at the end of the line in winter.

Local production and application of biomethane in industrial consumption centers in the middle or north of the country can improve the hydraulic balance of the system without the need to build pipelines.

The exact realization of this strategy and the use of its valuable side benefits such as "digested fertilizer" (digestite) as a complete substitute for chemical fertilizers and compliance with environmental standards require reference to the comprehensive biomass atlas of Satba and conducting more comprehensive feasibility studies.

It seems that the main reason for the lack of acceptance of this type of fuel lies in the subsidized energy pricing structure of the country. As long as fossil gas is available to industries at a low price, there will be no incentive for private sector investment.

Changing this situation requires reforming energy pricing and readjusting gas prices during peak hours based on real opportunity cost. Achieving this goal requires the use of existing legal tools, such as using the capacity of Article 12 of the Law on Removing Obstacles to Production, creating a green methane certificate market, and concluding bilateral purchase contracts between manufacturers and large industries.

If these mechanisms are connected to the guarantee of industrial gas supply in winter, biomethane can compensate part of the country's gas deficit during peak consumption and create a sustainable flow of energy from today's polluting waste.