Effects of operational mode on particle size and number emissions from a biomass gasifier cookstove

Abstract

Interest in the size distribution of particles emitted from biomass cookstoves stems from the hypothesis that exposure to ultrafine particles is more detrimental to human health than exposure to accumulation mode or other size regimes. Previous studies have reported that gasifier cookstoves emit smaller particles than other cookstove designs under steady operating conditions. In the present study, the number size distribution of particles emitted from a forced-air gasifier cookstove was measured at 1 Hz as the stove transitioned between several steady and transient operating modes. During normal operation, when the stove functioned as a top-lit updraft gasifier, the distribution was bimodal, with peaks at 10 nm and 40 nm, when a pot of water was on the stove. The distribution became unimodal with a peak at 10 nm when the pot was removed. Once the fuel bed had completely gasified and the secondary flame extinguished, the concentration of particles increased and the peak in number concentration shifted to approximately 80 nm. After refueling, when the stove operated as a conventional updraft gasifier, the peak in number concentration decreased to 10 nm. When the secondary flame extinguished a second time, the peak in number concentration increased to approximately 100 nm before decreasing to 20 nm during the char burnout phase. These results demonstrate that changes in operational mode influence the combustion process and produce distinct changes in the size distribution and rate of particle emissions.

A Laboratory Assessment of 120 Air Pollutant Emissions from Biomass and Fossil Fuel Cookstoves

“…In this study, we comprehensively characterized cookstove smoke profiles from a broad range of stove/fuel combinations to better understand cookstove emissions beyond PM 2.5 and CO. Although previous works have characterized CO, PM 2.5 , and bulk PM 2.5 composition (e.g., elemental carbon (EC), organic carbon, − and/or particle size − ), data for other constituents of cookstove smoke (e.g., speciated PAHs, VOCs, and carbonyl compounds) are not as widely available. For example, some studies report speciated emissions from stoves, but only characterize a limited number of compounds (e.g., only formaldehyde or benzo­[a]­pyrene , ) emitted by a limited number of stove/fuel combinations (e.g., one) and/or report few metrics (e.g., per-mass-fuel basis).…”

Cookstove Emissions and Performance Evaluation Using a New ISO Protocol and Comparison of Results with Previous Test Protocols

“…Only the Pellet stove showed statistically significant (but small) differences in average burning rates between ISO and WBT testing during high- and low-power phases. Pellet stove burning rates and firepower are largely controlled by the stove fan speed and combustion chamber diameter as opposed to fuel loading given the nature of fixed-bed combustion. , TSF and Wood Rocket stove fuel burning rates are largely controlled by fuel feeding by the operator. Average fuel burning rates for all stoves may be affected by differences between protocols in the duration of test phases.…”

The State of Access to Modern Energy Cooking Services

“…Additional in-depth research should focus on the emissions profile of pellet stoves and personal exposure of stove users. Pellet gasifiers have been shown to emit lower levels of PM 2.5 compared to traditional biomass stoves (with performance varying based on the pellet moisture content and user operations) (Champion and Grieshop 2019;Tryner, Volckens, and Marchese 2018). However, Task Team interviews indicate that it is possible that pellet gasifiers release other harmful emissions (e.g., ultrafine emissions).…”