Biomass Co-firing

Biomass co-firing is a promising technology to decrease the use of fossil fuels for energy generation and hence mitigate greenhouse gas emissions. Ministry of Power launched the National Mission on Use of Biomass in Thermal Power Plants which provides for biomass co-firing in Thermal Power Plants. But recently the unavailability of biomass pellets in hindering progress. Read here to learn more about biomass co-firing.

Ministry of Power launched the National Mission on Use of Biomass in Thermal Power Plants (rechristened as SAMARTH) which provides for co-firing of biomass waste in Thermal Power Plants.

The idea is to endeavor to convert the challenges of stubble burning into an opportunity for green power production and income generation for farmers & small entrepreneurs.

SAMARTH has been taking the lead in resolving the problems being encountered in enabling a smooth transition of thermal power plants into the biomass co-firing regime.

What is biomass co-firing?

Biomass co-firing is a promising technology to decrease the use of fossil fuels for energy generation and hence mitigate greenhouse gas emissions.

• Biomass is non-fossilized and biodegradable organic material originating from plants, animals, and microorganisms.
• This shall include products, by-products, residues, and waste from agriculture, forestry, and related industries as well as the non-fossilized and biodegradable organic fractions of industrial and municipal wastes.
• Biomass also includes gases and liquids recovered from the decomposition of non-fossilized and biodegradable organic material.

Biomass co-firing stands for adding biomass as a partial substitute fuel in high-efficiency coal boilers.

• Coal and biomass are co-combusted in boilers that have been designed to burn coal.
• For this purpose, the existing coal power plant has to be partly reconstructed and retrofitted.
• Co-firing is an option to convert biomass to electricity, efficiently and cleanly, and to simultaneously reduce greenhouse gas emissions of the power plant.

Advantages

• Biomass co-firing is a good method to minimize greenhouse gases, because this process reduces net CO₂, CH₄, SO_X, and often NO_X emissions, compared to coal combustion.
• The existing coal power plants can be retrofitted quickly and cost-effectively.
• Substituting 5-7 percent of coal with biomass in coal-based power plants can save 38 million tonnes of carbon dioxide emissions.
• Through the studies, it has been well established that 5% to 10% of biomass can be safely co-fired with coal in TPPs without any adverse impact on the power plant.

Challenges

Biomass co-firing also faces some challenges, like fuel supply, handling, and storage.

• There is also a potential increase in corrosion and some ash deposition issues.
• If not carefully designed, co-firing involves some risks, like increased plant outages, and possible interference with the operation of the burner, furnace, boiler, etc.
• In general, biomass is more expensive than coal. Even if biomass residues are used, which are available for free, these must be transported and pre-treated.
• It is challenging to store biomass pellets for long durations at the plant sites since they absorb moisture from air quickly, rendering them useless for co-firing.

Biomass co-firing processes

There are three different concepts for co-firing biomass in coal boilers:

Direct co-firing

• The biomass and the coal are burned in the same furnace.
• The mills for the grinding of the fuel and the burners may be the same as or be separate from the coal feeding. This depends on the biomass used and its fuel properties.
• This concept is most commonly used because it is the easiest to implement and most cost-effective.
• The biomass energy fraction is typically limited to below 10-20 %. For a high blend rate and the best performance, pre-treated fuels (e.g., white or black pellets) are used.

Indirect co-firing

• The solid biomass is converted to a clean fuel gas, using a biomass gasifier.
• The gas can be burnt in the same furnace as the coal.
• For this reason, it is also possible to use biomass, which, for example, is difficult to grind.
• The gas can be cleaned and filtered before use, to remove impurities.
• This principle is less used compared to direct co-firing.

Parallel co-firing

• It is also possible to install a completely separate biomass boiler in addition to the conventional boiler.
• In this case, the biomass boiler provides energy to the feed water or generates steam at low temperatures, while the conventional boiler tops up the superheat.

Biomass co-firing in India

In India, biomass pellets are available at much lower prices as compared to the sharply rising prices of imported coal.

• As power plants are facing a coal-shortage scenario, the significance of biomass has increased considerably.
• Hence, co-firing biomass pellets has become both environment-friendly as well as an economical option for power utilities as compared to the blending of imported coal.
• This is expected to give further impetus to the biomass pellet manufacturing sector.

Ministry of Power launched the National Mission on Use of Biomass in Thermal Power Plants (rechristened as SAMARTH) which provides for co-firing of biomass waste in Thermal Power Plants.

SAMARTH (Sustainable Agrarian Mission on use of Agro-residue in Thermal Power Plants) has been taking the lead in resolving the problems being encountered in enabling a smooth transition of thermal power plants into the biomass co-firing regime.

Biomass has been notified under Priority Sector lending by the RBI.

• This would enable easier & faster availability of bank loans to the pellet manufacturers.
• The State Bank of India has launched a dedicated scheme to provide long-term loans to pellet manufacturers.

Challenges

Even after many steps, India’s target for green coal power plants is challenged.

• The unavailability of biomass pellets of agricultural residues is emerging as a dampener in implementing the idea fully.
• Around 95,000-96,000 tonnes of biomass pellets are required per day for co-firing, but India’s pellet manufacturing capacity is 7,000 tonnes per day at present despite a surplus of 228 million tonnes of agricultural residue available in the country.
• Biomass pellet suppliers fetch better prices from other industries like textile, food processing, metal-based, or in the open market hence the bulk of it is being diverted.
• In many coal plants after successful trial runs also, co-firing is being done only intermittently based on the availability of biomass.
• The huge demand-supply gap is also due to the seasonal availability and unreliable supply of biomass pellets to the utility.

Biomass demand from industries escalated since the Commission for Air Quality Management in the National Capital Region and Adjoining Areas directed industries in the Delhi-National Capital Region to switch to cleaner fuels by end of September 2022.

Way forward

The Indian government has stressed increasing the capacity of pellet manufacturers and several pieces of training for pellet manufacturers have been conducted by the National Power Training Institute all over the country.

To further strengthen and regulate the supply chain, the manufacturers were also asked to be registered under SAMARTH.

With the participation of farmers along with private and public sectors of the industry, India will be able to take the Biomass cofiring and carbon footprint reduction in thermal power generation to the next level.

It is reported that biomass co-firing can help cut emissions from the thermal power sector by 90-180 million tonnes by 2030, replacing 50-100 million tonnes of coal.

-Article written by Swathi Satish