Search

We present an emission inventory of primary black carbon (BC) and primary organic carbon (OC) aerosols from fossil fuel and biofuel combustion between 1850 and 2000. We reconstruct fossil fuel consumption and represent changes in technology on a national and sectoral basis. Our estimates rely on new estimates of biofuel consumption, and updated emission factors for old technologies. Emissions of black carbon increase almost linearly, totaling about 1000 Gg in 1850, 2200 Gg in 1900, 3000 Gg in 1950, and 4400 Gg in 2000. Primary organic carbon shows a similar pattern, with emissions of 4100 Gg, 5800 Gg, 6700 Gg, and 8700 Gg in 1850, 1900, 1950, and 2000, respectively. Biofuel is responsible for over half of BC emission until about 1890, and dominates energy-related primary OC emission throughout the entire period. Coal contributes the greatest fraction of BC emission between 1880 and 1975, and is overtaken by emissions from biofuel around 1975, and by diesel engines around 1990. Previous work suggests a rapid rise in BC emissions between 1950 and 2000. This work supports a more gradual increase between 1950 and 2000, similar to the increase between 1850 and 1925; implementation of clean technology is a primary reason. [ABSTRACT FROM AUTHOR]

This paper presents annual, country-level estimates of biofuel use for the period 1850-2000. We estimate that global biofuel consumption rose from about 1000 Tg in 1850 to 2460 Tg in 2000, an increase of 140%. In the late 19th century, biofuel consumption in North America was very high, ∼220–250 Tg/yr, because widespread land clearing supplied plentiful fuelwood. At that time biofuel use in Western Europe was lower, ∼180–200 Tg/yr. As fossil fuels became available, biofuel use in the developed world fell. Compensating changes in other parts of the world, however, caused global consumption to remain remarkably stable between 1850 and 1950 at ∼1200 ± 200 Tg/yr. It was only after World War II that biofuel use began to increase more rapidly in response to population growth in the developing world. Between 1950 and 2000, biofuel use in Africa, South Asia, and Southeast Asia grew by 170%, 160%, and 130%, respectively. [ABSTRACT FROM AUTHOR]

China has been placing a substantial focus on biogas for reducing energy consumption and carbon dioxide (CO 2) emissions. The operation mode of biogas systems may make the CO 2 reduction target over-optimistic. There is limited research to investigate the influential factors that may be causing the gap between the actual and theoretical CO 2 reduction costs of biogas systems in China. In this research, by using field survey data of 209 biogas users and 489 non-biogas users from 19 villages in 2015, the gap between actual and theoretical unit CO 2 reduction cost is quantified at approximately 156 USD/t CO 2. By employing the Logarithmic Mean Divisia Index I (LMDI) model, it is found that both the cost effect (48%) and the reduction effect (52%) contribute to the unit CO 2 reduction cost gap. Four influential factors–household labor, accessibility to the energy resource, acceptance of biogas technology, and subsidy–significantly narrow the gap between actual and theoretical CO 2 reduction costs, while the levelized subsidy contributes to widening the gap. On average, biogas systems should be operated for at least four years and the substitution rate should be more than 67% in order to keep the gap between actual and theoretical CO 2 reduction costs under 50%. • Actual and theoretical CO 2 reduction costs of biogas systems are assessed. • The gaps are decomposed to the cost effect and the reduction effect. • Five key influential factors are investigated to narrow the gap. • The under-estimated CO 2 reduction costs of biogas systems are evaluated. [ABSTRACT FROM AUTHOR]

Abstract: We present global emission projections of primary particulate matter (PM) from exhaust of on-road vehicles under four commonly-used global fuel use scenarios from 2010 to 2050. The projections are based on a dynamic model of vehicle population linked to emission characteristics, SPEW-Trend. Unlike previous models of global emissions, this model incorporates more details on the technology stock, including the vehicle type and age, and the number of emitters with very high emissions (“superemitters”). However, our estimates of vehicle growth are driven by changes in predicted fuel consumption from macroeconomic scenarios, ensuring that PM projections are consistent with these scenarios. Total emissions are then obtained by integrating emissions of heterogeneous vehicle groups of all ages and types. Changes in types of vehicles in use are governed by retirement rates, timing of emission standards and the rate at which superemitters develop from normal vehicles. Retirement rates are modeled as a function of vehicle age and income level with a relationship based on empirical data, capturing the fact that people with lower income tend to keep vehicles longer. Adoption dates of emission standards are either estimated from planned implementation or from income levels. We project that global PM emissions range from 1100 Gg to 1360 Gg in 2030, depending on the scenario. An emission decrease is estimated until 2035 because emission standards are implemented and older engines built to lower standards are phased out. From 2010 to 2050, fuel consumption increases in all regions except North America, Europe and Pacific, according to all scenarios. Global emission intensities decrease continuously under all scenarios for the first 30 years due to the introduction of more advanced and cleaner emission standards. This leads to decreasing emissions from most regions. Emissions are expected to increase significantly in only Africa (1.2–3.1% per year). Because we have tied emission standards to income levels, Africa introduces those standards 30–40 years later than other regions and thus makes a remarkable contribution to the global emissions in 2050 (almost half). All Asian regions (South Asia, East Asia, and Southeast Asia) have a decreasing fractional contribution to global totals, from 32% in 2030 to around 22% in 2050. Total emissions from normal vehicles can decrease 1.3–2% per year. However, superemitters have a large effect on emission totals. They can potentially contribute more than 50% of global emissions around 2020, which suggests that they should be specifically addressed in modeling and mitigation policies. As new vehicles become cleaner, the majority of on-road emissions will come from the legacy fleet. This work establishes a modeling framework to explore policies targeted at that fleet. [Copyright &y& Elsevier]