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Exposure to particles with aerodynamic diameters less than 2.5 μm is estimated to cause significant morbidity and mortality worldwide leading many countries to develop ambient air pollution standards and guidelines. At local scales, community and environmental justice groups are also concerned about PM 2.5 concentrations that may be elevated above regional concentrations typically measured by centrally located monitors and standards as well. In an attempt to develop a low cost, easy to use monitor we evaluated a low-cost optical particle counter, the Dylos™, as a fine particulate mass sensor. Modified into a system called the Berkeley Aerosol Information Recording System (BAIRS), we compared performance against standard commercial instruments in chambers using polystyrene latex spheres, ammonium sulphate, and woodsmoke and in an urban ambient setting. Overall we find that the limit of detection of the BAIRS is less than 1 μg m (-3) and the resolution is better than 1 μg m(-3) for PM 2.5. The BAIRS sizes small (<0.5 μm) particles, and is able to accurately estimate the mass concentration of particles of varying composition including organic, inorganic, and ambient particles. It is able to measure concentrations up to 10.0 mg m (-3). In an ambient roof-top test of the BAIRS and a more expensive commercially available light scattering particle monitor the BAIRS response tracked well with the commercial monitor and daily means were within 80% of each other. We conclude that with appropriate modification the system could be developed into an accurate low cost realtime particle mass monitor for use in a wide range of applications.

In spite of growing interest, a principal obstacle to wider inclusion of improved cookstove projects in carbon trading schemes has been the lack of accountability in estimating CO 2 -equivalent (CO 2 -e) savings. To demonstrate that robust estimates of CO 2 -e savings can be obtained at reasonable cost, an integrated approach of community-based subsampling of traditional and improved stoves in homes to estimate fuel consumption and greenhouse gas emissions, combined with spatially explicit community-based estimates of the fraction of nonrenewable biomass harvesting (fNRB), was used to estimate CO 2 -e savings for 603 homes with improved Patsari stoves in Purépecha communities of Michoacán, Mexico. Mean annual household CO 2 -e savings for CO 2 , CH 4 , CO, and nonmethane hydrocarbons were 3.9 tCO 2 -e home -1 yr -1 (95% CI ( 22%), and for Kyoto gases (CO 2 and CH 4 ) were 3.1 tCO 2 -e home -1 yr -1 (95% CI ( 26%), respectively, using a weighted mean fNRB harvesting of 39%. CO 2 -e savings ranged from 1.6 (95% CI ( 49%) to 7.5 (95% CI ( 17%) tCO 2 -e home -1 yr -1 for renewable and nonrenewable harvesting in individual communities, respectively. Since emission factors, fuel consumption, and fNRB each contribute significantly to the overall uncertainty in estimates of CO 2 -e savings, communitybased assessment of all of these parameters is critical for robust estimates. Reporting overall uncertainty in the CO 2 -e savings estimates provides a mechanism for valuation of carbon offsets, which would promote better accounting that CO 2 -e savings had actually been achieved. Cost of CO 2 -e savings as a result of adoption of Patsari stoves was US$8 per tCO 2 -e based on initial stove costs, monitoring costs, and conservative stove adoption rates, which is ∼4 times less expensive than use of carbon capture and storage from coal plants, and ∼18 times less than solar power. The low relative cost of CO 2 -e abatement of improved stoves combined with substantial health cobenefits through reduction in indoor air pollution provides a strong rationale for targeting these less expensive carbon mitigation options, while providing substantial economic assistance for stove dissemination efforts. IntroductionThere is growing interest in trading carbon offsets from improved stove programs on carbon markets for voluntary reductions, or as part of the Clean Development Mechanism (CDM) of the Kyoto Protocol. This interest arises from the large number of people that still cook with biomass (approximately half of the global population) (1), and because emissions of greenhouse gases (GHGs) relative to delivered energy are high as a result of poor total energy efficiency of traditional stoves. There are three principal barriers to more widespread acceptance of carbon offsets from improved biomass cookstove projects. First, measurement and verification of emissions reductions are complex compared to the stack monitors typically used for industrial facilities, as stoves are spread over large areas, often in remote regions. Traditional assess...

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Monitoring and evaluation of improved cookstove performance is a critical factor in program success; however, consistent evidence indicates water boiling tests and controlled cooking tests are not representative of stove performance during daily cooking activities, and there is no ability to link these tests to kitchen performance tests during normal daily cooking activities. Since emissions from cookstoves contribute heavily to regional estimates of carbonaceous aerosols and other short-lived greenhouse species and given the current importance of stove performance tests as a basis for global climate prediction models and IPCC inventories, improvements in performance testing are critical to derive more representative estimates. Here real-time combustion efficiencies and emissions rates from daily burn cycles of open fires and improved stoves in Mexico are used to propose a new approach to stove performance testing, using simple and economical measurement methods, based on replication of the distribution of emission rates and combustion efficiencies seen during daily cooking activities in homes. This approach provides more relevant information for global climate models and inventories, while also providing a means to recreate representative emissions profiles in a laboratory setting for technical analyses. On the basis of emission rates and combustion efficiencies during normal daily cooking, we suggest performance criteria that can be used as benchmarks for laboratory testing of improved stoves in the absence of site-specific information, although requiring confirmation by field testing during daily cooking activities.

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