Contributors to this blog: Claire Squire, Thomas C. Hilde, Jiehong Lou, Lauren Lohff

Indonesia’s greenhouse gas emissions are the sixth largest in the world (Climate Watch, 2024). While the majority of these emissions come from land use change, a growing fraction is attributed to its electricity sector, which is dominated by coal. Decarbonizing Indonesia’s coal fleet faces many challenges: the fleet is young, risking considerable stranded assets and raising the cost of early retirement; the price of coal, which is produced domestically, is kept artificially low; and the fleet is projected to grow by nearly 15 GW by 2030, driven by expansion of captive coal in powering industry. Given the difficulty of retiring coal plants, and the availability of abundant biomass resources, biomass co-firing presents a potential opportunity to reduce coal plant emissions using existing infrastructure and domestic energy supply. 

In 2020, Perusahaan Listrik Negara (PLN), Indonesia’s state-owned electricity company, alongside the Ministry of Energy and Mineral Resources, announced plans to begin co-firing biomass (Adhiguna, 2021). Recent updates to the co-firing policy call for the use of nine million tons of biomass by 2030 (Republic of Indonesia, 2022) and specify that nearly 19 GW of capacity should co-fire by 2050 (PLN, 2022). Biomass co-firing, the blending of biomass and coal in coal boilers for combustion and electricity generation, is a mature technology used across the world, one proffered to provide emissions reductions according to the biomass share used. However, the emissions profile of this strategy depends upon the source of the biomass. Using biomass purpose-grown on plantations risks inducing deforestation to clear lands to meet bioenergy needs at coal plants, thereby moving emissions from coal plants to the land sector. 

In our analysis recently published in Nature’s Communications Earth & Environment, we assess the ability of biomass wastes - residues from other industries, including agriculture, forestry, and manufacturing - to meet a range of co-firing ratios at coal plants across Indonesia. We consider waste residues to be nearly carbon neutral, as they are byproducts from existing industries and thus do not induce land use change for their specific use in coal plants.

Our Approach:

We conducted a province-level analysis of plant-level biomass demand, considering both captive and on-grid coal plants, involving a total capacity of 43.4 MW in 2023. On the supply side, we calculated province-level supply of waste feedstocks including palm kernel shells, empty oil palm fruit bunches, rice straw, rice husk, municipal solid waste, rubber wood, wood waste, and bagasse. To determine availability, we calculated feedstocks produced monthly in each province, noting the quantity diverted to other uses, including as processing fuel, fertilizer, or exports as well as losses associated with biomass decay. We then calculated the emissions reductions possible under a range of blending ratios, which we varied by boiler type (considering circulating fluidized bed (CFB), stoker, and pulverized coal (PC) plants) in accordance with their technical capabilities.

Given the risk of land-use impacts alongside limited waste availability, we find that biomass co-firing has limited potential to reduce coal plant emissions.

We examined the ability of biomass wastes to meet a range of demand scenarios, and associated emissions reductions. We find that: 

1. Existing biomass waste supply can only support low-ratio co-firing. In the mid and high co-firing scenarios, we find a deficit between available biomass and the quantity demanded at coal plants.

2. After accounting for diversions to other uses, only 30.7% of biomass wastes remain for use in co-firing. Residues are primarily used as fertilizer and as processing fuel, but a large share of palm kernel shells are exported, a trend that is expected to grow among energy-dense feedstocks.

3. Gaps between biomass supply and demand are most pronounced in eastern Indonesia, where captive coal capacity continues to grow. Biomass wastes are most abundant on the islands of Sumatra and on Borneo, while the island of Sulawesi, the Moluccas, and parts of Java struggle to supply their coal plants. Inter-island trade routes have the potential to alleviate some of this deficit, but not cannot completely eliminate it.

4. Seasonal variation in waste production poses challenges in some regions. Seasonal variation in biomass availability increases the deficit between plant-level demand and provincial supply in some months. Overcoming this barrier and expanding overall bioenergy use will require increased investment in storage infrastructure.

5. Emissions reductions from co-firing are unable to offset fleet growth except at levels that waste feedstocks cannot supply. Preliminary analysis of using purpose-grown bioenergy, specifically wood pellets, for co-firing finds that substantial emissions would result.

Further research is needed to determine cost and emissions associated with the collection, transportation, and storage of biomass, as well as the coal plant retrofits needed to enable broad-scale co-firing. However, limited policy guidance currently exists to guide implementation of co-firing, and our preliminary analysis indicates that the potential for emissions reductions using wastes and risk of driving further deforestation using purpose-grown biomass limits its viability as a mitigation strategy.

Reference

Adhiguna, P. Indonesia’s Biomass Cofiring Bet: Beware of Implementation Risks. https://ieefa.org/resources/indonesias-biomass-cofiring-bet-beware-implementation-risks (2021).

Climate Watch. Historical GHG Emissions. https://www.climatewatchdata.org/ghg-emissions (2024).

PLN. Green Economy Program in Power Industry Towards Net Zero Emission. PLN Energi Primer Indonesia https://mebi.or.id/wp-content/uploads/2023/02/BIOMASS-CO-FIRING-PROGRAM-TOWARDS-NET-ZERO-EMISSION_PLN-EPI.pdf (2022).

Republic of Indonesia. Enhanced Nationally Determined Contribution Republic of Indonesia. https://unfccc.int/sites/default/files/NDC/2022-09/23.09.2022_Enhanced%20NDC%20Indonesia.pdf (2022).