Solid biofuel — pellets, briquettes and residue fuels — instead of coal in boilers and kilns

Replaces: coal/HFO in boilers, straw burning in fields · Scope: pellets, briquettes, co-firing · Evidence: high

The chemical problem#

• Coal carries sulfur, mercury and ash into boilers — and every tonne is fossil carbon.
• Every harvest leaves straw, husk, shell and stalk residues that are burned in the open (Delhi’s winter smog episodes, Egyptian rice-straw burn-offs) or left to rot to methane.
• Heavy fuel oil in dryers and kilns completes the fossil slate for exactly the heat duties residues could serve.

Product overview#

1. Pellets and briquettes: dried, milled residues extruded to dense, storable, transportable fuel (6 mm industrial pellets, 60–90 mm briquettes); standard fuel specs (EN ISO 17225 classes) exist for trade.
2. Boiler-side practice: biomass boilers and co-firing (5–30 % share) in existing coal units — the lowest-capex decarbonization step many plants have.
3. Kiln and dryer duty: briquettes replace coal/HFO in brick kilns, lime, grain and tobacco drying — the classic small-industry conversions of South Asia and Africa.
4. Circular variants: pellet plants co-located with sugar mills, sawmills and rice processors (the residue arrives at the gate; EN02’s mill logic).

Active ingredient / Composition#

• Lignocellulosic biomass: 15–19 MJ/kg dry (≈ half of coal volumetrically, similar per-tonne-C); ash 1–8 % (straw higher — additive/clinker management).
• Binders usually none (lignin self-binds under extrusion heat/pressure).

Key facts#

• | Co-firing | 5–20 % share typically needs burner/feed retrofits only |

Advantages#

• Waste-to-heat with local fuel security: no import line, price set by collection logistics, not world coal.
• Kills the open-burning smog problem by giving the straw a buyer (the same tonne, two problems solved).
• Boilers and kilns convert at modest capex; co-firing exists precisely as a bridge technology.
• The biomass-waste-to-value cluster (176 active companies in this index) is the regionally strongest supplier base of the whole energy collection.

Mode of action#

• Combustion physics unchanged: fixed-carbon burn plus volatiles; the substitution is fuel chemistry (biogenic carbon, near-zero sulfur, low mercury) and logistics (densification makes residue a commodity).

Application#

• | Municipality | Smog control | Straw-purchase pellet plants in burning districts |

Limitations#

• Ash and slagging: straw-rich fuels need additives/boiler tuning; chlorine corrosion in some designs.
• Seasonality and low bulk density make haulage the cost boss — plants must sit on the residue.
• Not a route for the highest-temperature kilns or blast furnaces (Partial verdict there).
• Sustainability rules (land, competition with soil carbon return) apply to residue removal rates.

Evidence of displacement — D2: measurable displacement (minority share)#

Assessment (hand-reviewed): UK coal down 85% since 2013, partly via conversion to biomass (IEA Bioenergy). Brazil: sugar-mill bagasse power grew from ~100 MW (2000) to ~12.4 GW (2023, ANEEL via ISO); 266 of 422 certified mills export power to the grid.

Figures found (verified as quoted, but the assessment above explains why they do not count as displacement evidence for this substitution):

• displacement — In the UK, coal consumption dropped by 85% since 2013, with part of this reduction achieved through the conversion of existing coal power plants to biomass. (UK, 2013-2019; government or intergovernmental: ieabioenergy.com)
• displacement — In Brazil, 170 sugar mills currently export surplus bioelectricity to the grid. (Brazil, not specified; peer-reviewed: sciencedirect.com)
• displacement — Less than 10% of India’s estimated potential for bagasse cogeneration has been exploited. (India, 2004; peer-reviewed: exa.ai)
• displacement — Brazil is the global leader in bagasse-based cogeneration, with installed capacity increasing from approximately 100 MW in 2000 to 12,425 MW in 2023. (Brazil, 2000-2023; weak: isosugar.org)

Suppliers — real products and services (from the vendor index)#

Active vendors matched by topic tags (biomass-waste-to-value, 176 active companies); open each card for evidence, contacts and status.

Government funding signals#

Scanned 2026-09-28 (OpenAIRE + NSF); candidates reviewed by hand.

Signal: none in research councils — support arrives as renewable-heat incentives and air-quality policy. Pellet supply chains are infrastructure, not research objects; the straw-burning smog problem drives public money via agricultural-residue programs and boiler-conversion subsidies rather than grants databases.

Scientific evidence#

• Selkimäki M, Mola-Yudego B, Röser D, Prinz R, Sikanen L (2010). Present and future trends in pellet demand, markets and prices in Finland and Sweden. Energy Policy 38: 6986–6995.
• Note: journal references will be checked against Crossref by the automated pass.

Bioeconomy value#

The substitution where the pollution problem and the fuel supply are the same physical object — the straw that would smoke a city can fire its brick kilns, with the residue-handling vendor base of this index moving it.

Fifth article of energy — completes the collection’s planned set. Cross-links: mill residues ↔ EN02/EN03; biogas from wet residues ↔ EN01; ash-to-soil ↔ A35.