In the perspective of energy sustainability, biomass is the widely used renewable domestic energy with low cost and easy availability. Increasing studies have reported the health impacts of toxic substances from biomass burning emissions. To make proper use of biomass as residential solid energy, the evaluation of its health risks and environmental impacts is of necessity. Empirical studies on the characteristics of toxic emissions from biomass burning would provide scientific data and drive the development of advanced technologies. This review focuses on the emission of four toxic substances, including heavy metals, polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), and volatile organic compounds (VOCs) emitted from biomass burning, which have received increasing attention in recent studies worldwide. We focus on the developments in empirical studies, methods of measurements, and technical factors. The influences of key technical factors on biomass burning emissions are combustion technology and the type of biomass. The methods of sampling and testing are summarized and associated with various corresponding parameters, as there are no standard sampling methods for the biomass burning sector. Integration of the findings from previous studies indicated that modern combustion technologies result in a 2–4 times reduction, compared with traditional stoves. Types of biomass burning are dominant contributors to certain toxic substances, which may help with the invention or implementation of targeted control technologies. The implications of previous studies would provide scientific evidence to push the improvements of control technologies and establish appropriate strategies to improve the prevention of health hazards.

Distinguished features of cities influence the characteristics of CH4 emissions. A city-level emission inventory represents the characteristics of CH4 on a smaller scale, according to the special factors in each city. A city-level emission inventory was established to reveal the characteristics and source profile of CH4 emissions in the coldest province, which is a typical provincial cold region in northeast China. The dominant sources were identified for targeted cities. Rice cultivation, coal mining, oil and gas exploitation, and livestock are the dominant emission sectors. Emissions from other sectors, including wastewater disposal, biomass burning, landfill, etc. were also estimated. The provincial CH4 emissions increased gradually from 2003 to 2012, up to 2993.26 Gg with an annual increase rate of 2.85%; the emissions were 2740.63 in 2020. The emissions of CH4 in Harbin, Daqing, Jiamusi, and Hegang cities were higher than in the other nine cities, which were 337.23 Gg, 330.01 Gg, 328.55 Gg, and 307.42 Gg in 2020, respectively. Agriculture, including the rice cultivation, livestock, and biomass burning sectors contributed to 51.24–62.12% of total emissions, and the contributions increased gradually. Coal mining, oil and gas exploration, and fossil fuel combustion are energy-related sources, which contributed up to 37.91% of the total emissions, and the proportion kept decreasing to 23.87% in 2020. Furthermore, meteorological factors are especially relevant to the region, by which the differences of ambient temperature are over 60 °C (±30 °C). In the summer, CH4 emissions from the rice cultivation, biomass burning, livestock, and landfill sectors are obviously distinct from the heating period (winter), while few differences in CH4 emissions are found from wastewater disposal and the fossil fuel production sectors.

Energy production and consumption are dominant sources of CO2 emissions. Investigating the amount and characteristics of CO2 emission sources can aid in reducing CO2 emissions from energy-related sectors, which could lead to the development of advanced technologies and ideas for abatement. Cities play a significant role in CO2 emissions, representing a distinctive unit with a specialized energy consumption structure, meteorology, economy, agriculture, forest acreage, etc. Those properties interact and influence CO2 emissions. The city-level emission inventory is an important scientific database helping to investigate emission abatement technologies and establish control strategies. In this study, city-level CO2 emissions and ecological absorption of China’s coldest province are quantified. In the targeted region, winter lasts for about 6 months. Sectors of industry, thermal power generation, and domestic heating are dominant contributors to the total emissions. The provincial CO2 emissions from energy consumption increased gradually, reaching 327.61 million tons in 2019. Cities with strong industrial activities produced higher CO2 emissions. Moreover, the targeted region is a strong agriculture province, with the largest contribution to grain production in China. The absorption of farmland and forest was quantified, at 343.91 and 69.3 million tons in 2019, respectively. The total absorption was higher than the energy-related emissions. This indicated that the targeted region would provide a considerable carbon sink, attributed to the properties of its ecological system. From 2017 onwards, small boilers (single boilers smaller than 32 steam tons) were removed, and hence the emissions were lower than the original value. This study presents the characteristics of CO2 emissions, and reveals the co-benefit of air pollution control on CO2 reduction.