# How much CO2 does a chemical dryer save by switching a wood-fired hot air generator to gas?

Canonical: https://senseible.earth/answers/gas-hot-air-generator-replacing-wood-dryer-co2

It raises your reported fossil CO2, by about 35 t a year on BEE's Ahmedabad figures. A 30,000 kcal/h gas unit replaces 130 t of wood with 14,940 Nm3 of gas and adds 6,040 kWh. Wood CO2 is biogenic and reported separately, so the report's 93 t cut does not belong in Scope 1.

## What BEE's Ahmedabad report measured

- A wood-fired hot air generator feeding one 200-tray dryer burns about 36 kg of wood an hour, around 130 t a year.
- Measured heat out was 35,964 kcal/h against 97,200 kcal/h of wood in, an efficiency of about 37%.
- The proposed 30,000 kcal/h gas unit burns 4.15 Nm3 an hour, 14,940 Nm3 a year, with a 2 hp blower and air out at up to 150 C.
- Electricity rises by about 6,040 kWh a year.
- Project cost Rs 2.50 lakh, saving Rs 0.76 lakh a year, simple payback 3.29 years, at 2010 prices.

## Why the report's 93 t cut is not yours to claim

The report counts 130 t of wood as 123 t of CO2 avoided, subtracts 30 t for the gas, and calls the difference a 93 t reduction. Under the GHG Protocol, CO2 from burning wood is biogenic: you report it separately, outside the Scope 1 total. Gas is fossil and goes inside it.

So the switch takes your Scope 1 from close to zero for this dryer to about 31 t, and Scope 2 up by about 4 t. Methane and nitrous oxide from burning wood do stay in Scope 1, but they are small, so removing them barely moves the total.

## Good reasons to switch anyway

- Steady air temperature, which the report links to drying quality.
- No wood logs to store, size and feed by hand.
- Less pressure on local forests, which the report flags because much of the wood is not from renewable sources.
- If the wood is cut from forest that is not replanted, write that in a note to your inventory. Do not net it off your Scope 1 figure.

## What to check before you order

- Gas supply and pressure for 4.15 Nm3 an hour at your site, and a separate gas meter on the new unit.
- Whether your supplier bills in Nm3 (at 0 C) or scm (usually 15 C); the two differ by about 5%.
- Your own wood use per hour over a full week, weighed, before you compare running costs at today's prices.

## One 200-tray dryer for a year, before and after

- Before: 130 t of wood. CO2 from it is biogenic, reported separately. Fossil CO2 for this dryer: close to zero
- After, gas: 14,940 Nm3 x 2.05 kg CO2 per m3 = 30.6 t CO2 (Scope 1)
- After, extra power: 6,040 kWh x 0.675 = 4.1 t CO2 (Scope 2)
- Change in reported fossil CO2: about 34.7 t more a year

Gas at our natural gas factor of 2.05 kg CO2 per cubic metre; LNG delivered as gas is natural gas. Grid factor is CEA's for FY 2025-26. Both are estimates.

## What Senseible does here

Senseible reads your gas and electricity bills and gives monthly CO2 for each with the factor named, so the effect of a dryer switch shows up line by line in your records. The green loan check shows what a lender will want to see for the new unit.

- [Green loan readiness check](https://senseible.earth/green-loan-check)
- [Biomass boilers: methane and N2O stay in Scope 1](https://senseible.earth/answers/biomass-boiler-ch4-n2o-still-scope-1)
- [Ahmedabad chemical cluster footprint](https://senseible.earth/answers/ahmedabad-chemical-cluster-gas-carbon-footprint)
- [Biomass gasifier or LPG for a dryer](https://senseible.earth/answers/biomass-gasifier-vs-lpg-furnace-emissions)

Sources: [BEE, Detailed project report: energy efficient gas fired hot air generator 30,000 kcal/h, Ahmedabad chemical cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/dpr/Ahmedabad_30000.pdf), [GHG Protocol Corporate Standard (biogenic CO2 reported separately)](https://ghgprotocol.org/corporate-standard), [IPCC 2006 Guidelines, Volume 2 Energy, Tables 1.2 and 2.3](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html), [CEA CO2 Baseline Database, version 22.0](https://cea.nic.in/cdm-co2-baseline-view?mappingId=234&lang=en)

Last reviewed 2026-10-31. Report figures are from a BEE SME programme project report; costs and paybacks are at the report year's prices. Check today's fuel and power prices before you rely on the payback.