Calculating Greenhouse Gas Emissions from Cookstoves
Improved cookstoves emit less greenhouse gases (GHGs) than traditional cookstoves. The amount of GHG emissions reduced can vary according to four key variables, in order of importance: fuel type, device efficiency, non-renewable biomass and cooking practice.
- Fuel type – Emission factors define the amount of GHGs emitted when a particular fuel is burned to produce a given amount of cooking energy. For example, biomass and charcoal emit on average twice as much GHGs as LPG to produce the same amount of cooking energy. Solar cookers on the other hand do not produce any GHG emissions.
- Device efficiency – Device efficiency reflects how much fuel the stove consumes, how effectively it burns the fuel, and how long it takes to cook a meal. GHG emission reductions occur when a stove simply takes less fuel to cook, but also thanks to a more complete combustion of the fuel an efficient stove emits less gases into the atmosphere. Efficiency is calculated using laboratory and field tests to assess energy consumption of the cookstove. Energy savings are then determined by comparing the test results to a baseline scenario.
Information on the efficiency of various stove types can be found in the Clean Cooking Catalog.
- Non-renewable biomass – It is critical to assess whether biomass fuels used for cooking are collected primarily from renewable or non-renewable biomass sources. If biomass is sustainably harvested, greenhouse gases released in the combustion of the biomass fuel are considered to be balanced by greenhouse gases absorbed during the growth cycle of the plant material. This means that improved cookstoves only reduce GHG emissions when some part of the biomass consumed would not have grown back due to unsustainable depletion of biomass resources in the area. Hence, by reducing biomass consumption, improved cookstoves are reducing the amount of deforestation and/or biomass depletion in a region, thus making them eligible for carbon credits.In order to establish the non-renewable nature of woody biomass in a region, the CDM requires projects to demonstrate two of the following four criteria:
- A trend showing an increase in time spent or distance travelled for gathering fuelwood, by users (or fuelwood suppliers), or alternatively, a trend showing an increase in the distance the fuelwood is transported to the project area;
- Survey results, national or local statistics, studies, maps or other sources of information, such as remote-sensing data, which show that carbon stocks are depleting in the project area;
- Increasing trends in fuel wood prices indicating a scarcity of fuelwood;
- Trends in the types of cooking fuel collected by users that indicate a scarcity of woody biomass.
The fraction of woody biomass varies between 0 (meaning fully renewable biomass) and 1 (meaning fully non-renewable biomass due to increased depletion rates). The higher the fraction for a particular region is, the higher the GHG emission reductions achieved for projects from that region are, assuming all other factors remain the same.
- Cooking practice – This is the most complex variable to monitor because it varies across households, largely due to differences in daily usage of fire/fuel and variations in kitchen conditions/habits. In the recent past, carbon finance focused on fuel and efficiency to define the methodology used to control GHG emissions. Now, cooking practice is being increasingly recognized as an additional key element to be assessed because of its impact on health. The inclusion of cooking practice was recently accepted by a voluntary methodology (Gold Standard “Technologies and Practices that Displace Decentralized Thermal Energy Consumption”). Interest in this area remains, however, low due to its novelty status.