# How much wood does an efficient wood-fired hot air generator save over an old one?

Canonical: https://senseible.earth/answers/efficient-wood-hot-air-generator-saving

Sixteen kg of wood an hour, 36 down to 20, in BEE's Ahmedabad report: 57.6 t of wood a year over 3,600 hours. Cost Rs 3.03 lakh, payback 2.18 years (2010). Fossil CO2 rises about 3 t from the blower, because wood CO2 is biogenic; the report's 53 t cut is not Scope 1.

## Old heater against new

- Old: single pass, poor grate, high draught resistance. About 36 kg of wood an hour for 35,936 kcal of hot air; the report calls it 37% efficient in one place and around 32% in another.
- New 30,000 kcal an hour unit: three pass heat exchange, forced draught, controlled combustion, larger grate. About 20 kg of wood an hour.
- 12 hours a day, 300 days a year: 57,600 kg of wood saved.
- Blower load 1.86 kW, 6,696 kWh a year, which the report charges in full against the saving.

## Better wood heater or gas heater

- Efficient wood unit: Rs 3.03 lakh, Rs 1.39 lakh a year, 2.18 years. Fossil CO2 up about 3 t.
- Gas unit, from the same report series: Rs 2.50 lakh, Rs 0.76 lakh a year, 3.29 years. Fossil CO2 up about 35 t, because gas is fossil and wood is not.
- If a buyer is asking for lower Scope 1 and 2, the efficient wood unit keeps them lower. If the buyer or lender questions where your wood comes from, gas avoids that question but raises your reported total.

## What counts in your footprint

Wood CO2 is biogenic: report it separately. Methane and nitrous oxide from burning it stay in Scope 1, about 1.7 t CO2e for the 57.6 t saved. The blower's 6,696 kWh add about 4.5 t in Scope 2. Net, Scope 1 plus 2 rise by about 2.8 t.

## Checks before you buy

- Weigh wood fed per hour for a week on the old unit; the saving is measured from that number.
- Ask whether the old blower stays. If it is replaced, only the difference in kWh counts.
- Ask the supplier for the outlet air temperature and flow at your dryer's load.

## One hot air generator, one year (estimate)

- Wood saved: 16 kg x 12 h x 300 days = 57.6 t
- Money: 57.6 t x Rs 3,000 = Rs 1.73 lakh, less 6,696 kWh x Rs 5 = Rs 0.33 lakh: Rs 1.39 lakh
- Scope 1 avoided: 57.6 x 0.030 = 1.7 t CO2e; Scope 2 added: 6,696 x 0.675 = 4.5 t
- Biogenic CO2 avoided, reported separately: 57.6 x 1.75 = about 101 t

Wood at IPCC 2006 defaults with AR6 warming potentials; grid CEA FY 2025-26.

## What Senseible does here

Senseible reads electricity and gas bills into monthly CO2 records, which is where either choice shows up. It has no built-in wood factor, so add wood using the figures here. The green loan check shows what a lender needs for the new heater.

- [Green loan readiness check](https://senseible.earth/green-loan-check)
- [Wood to gas hot air generator](https://senseible.earth/answers/gas-hot-air-generator-replacing-wood-dryer-co2)
- [Efficient 96-tray dryer](https://senseible.earth/answers/efficient-tray-dryer-wood-saving-chemical-unit)
- [Membrane filter press](https://senseible.earth/answers/membrane-filter-press-drying-wood-saving)

Sources: [BEE, Detailed project report: energy efficient hot air generator 30,000 kcal/hr, Ahmedabad chemical cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/dpr/Ah_30000_1.pdf), [BEE, Detailed project report: gas fired hot air generator 30,000 kcal/hr, Ahmedabad chemical cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/dpr/Ahmedabad_30000.pdf), [IPCC 2006 Guidelines, Volume 2 Energy, Table 1.2 (net calorific values) and Chapter 2 tables](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html), [GHG Protocol Corporate Standard (biogenic CO2 reported separately from the scopes)](https://ghgprotocol.org/corporate-standard), [CEA, CO2 Baseline Database for the Indian Power Sector, version 22.0 (FY 2025-26 grid factor)](https://cea.nic.in/cdm-co2-baseline-view?mappingId=234&lang=en)

Last reviewed 2026-10-31. Equipment figures are from a BEE SME programme project report; costs and paybacks are at that report's prices. Recheck with today's fuel and power prices and a current quote.