Variations of anthropogenic CO2 in urban area deduced by radiocarbon concentration in modern tree rings

Radiocarbon concentration in the atmosphere is significantly lower in areas where man-made emissions of carbon dioxide occur. This phenomenon is known as Suess effect, and is caused by the contamination of clean air with non-radioactive carbon from fossil fuel combustion. The effect is more strongly observed in industrial and densely populated urban areas. Measurements of carbon isotope concentrations in a study area can be compared to those from areas of clear air in order to estimate the amount of carbon dioxide emission from fossil fuel combustion by using a simple mathematical model. This can be calculated using the simple mathematical model. The result of the mathematical model followed in this study suggests that the use of annual rings of trees to obtain the secular variations of 14C concentration of atmospheric CO2 can be useful and efficient for environmental monitoring and modeling of the carbon distribution in local scale.     

Carbon-14, tree rings,and urban air pollution

Differences in natural ¹⁴C content of rings from trees from urban and rural locations have been compared on a year by year basis. The differences as a fraction of the urban tree's radioactivity reflect the local excess ¹⁴C-free carbon dioxide from fossil fuel combustion in the urban environment. New York City, Boston, and Washington, D.C., show different degrees of excess carbon dioxide. New York City averages about 6% excess carbon dioxide between 1950 and 1970. From this is infered an average carbon monoxide concentration during this period of 5 ppm.     

Pollutant emission rates from indoor combustion appliances and sidestream cigarette smoke

Particulate and gaseous emissions from indoor combustion appliances and smoking can elevate the indoor concentrations of various pollutants. Indoor pollutant concentrations resulting from operating one of several combustion appliances, or from sidestream tobacco smoke, were measured in a 27-m³ environmental chamber under varying ventilation rates. The combustion appliances investigated were gas-fired cooking stoves, unvented kerosene-fired space heaters, and unvented natural-gas-fired space heaters. Results showed elevated levels of carbon dioxide, carbon monoxide, nitric oxide, nitrogen dioxide, formaldehyde, and suspended particles from one or more of the pollutant sources investigated. Our findings suggest that, of the sources examined in this study, nitrogen dioxide from combustion appliances and particles from sidestream cigarette smoke are the most serious contaminants of indoor air, if we use existing standards and guidelines as the criteria. An emission rate model was used to quantify the strengths of the pollutant sources, which are reported in terms of the mass of pollutant emitted per energy unit of fuel consumed (in the case of gas and kerosene appliances) and per mass of tobacco combusted (in the case of smoking).     

Global estimates of soil carbon sequestration via livestock waste: a STELLA simulation

It has become increasingly well documented that human activities are enhancing the greenhouse effect and altering the global climate. Identifying strategies to mitigate atmospheric carbon dioxide emissions on the national level are therefore critical. Fossil fuel combustion is primarily responsible for the perturbation of the global carbon cycle, although the influence of humans extends far beyond the combustion of fossil fuels. Changes in land use arising from human activities contribute substantially to atmospheric carbon dioxide; however, land use changes can act as a carbon dioxide sink as well. A soil carbon model was built using STELLA to explore how soil organic carbon sequestration (SOC) varies over a range of values for key parameters and to estimate the amount of global soil carbon sequestration from livestock waste. To obtain soil carbon sequestration estimates, model simulations occurred for 11 different livestock types and with data for eight regions around the world. The model predicted that between 1980 and 1995, United States soils were responsible for the sequestration of 444–602 Tg C from livestock waste. Model simulations further predicted that during the same period, global soil carbon sequestration from livestock waste was 2,810–4,218 Tg C. Our estimates for global SOC sequestration are modest in proportion to other terrestrial carbon sinks (i.e. forest regrowth); however, livestock waste does represent a potential for long-term soil carbon gain. SOC generated from livestock waste is another example of how human activities and land use changes are altering soil processes around the world. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

The global carbon cycle and possible disturbances due to man's interventions

Global atmospheric CO₂ concentration has increased since the beginning of reliable monitoring in 1958 at a mean rate of about 0.9 ppm CO₂/yr. Now, atmospheric CO₂ concentration is at 330 ppm. From about 1860 up to 1974, man's intervention in the global carbon cycle caused a likely increase of 76.6 × 10¹⁵ gC, corresponding to 36 ppm CO₂ in the atmosphere, if a preindustrial content of 294 ppm CO₂ or 625.3 × 10¹⁵ g C is adopted to be valid. A further rise of atmospheric CO₂ seems to be inevitable and probably will be responsible for a climatic warming in the next several decades; therefore, a global examination of carbon reservoirs and carbon fluxes has been undertaken to determine their storage capacity for excess carbon which orginated mainly from burning fossil fuels and from land clearing. During 1860–1974 about 136 × 10¹⁵ g C have ben emitted into the atmosphere by fossil fuel combustion and cement production. At present, the emission rate is about 5 × 10¹⁵ g C/yr. The worldwide examination of carbon release, primarily by deforestation and soil cultivation since 1860, is estimated to be about 120 × 10¹⁵ g C. The net transfer of carbon to the atmosphere owing to man's interference with the biosphere is now believed to be about 2.4 × 10¹⁵ g C/yr. An oceanic uptake of roughly 179 × 10¹⁵ g C since 1860 is open to discussion. According to the chemical buffering of sea surface water only about 35.5 × 10¹⁵ g C could have been absorbed. It is argued, however, that oceanic circulations might have been more effective in removing atmospheric excess carbon of anthropogenic origin.     

Energy Use and CO2 Production in Tropical Agriculture and Means and Strategies for Reduction or Mitigation

Carbon dioxide emissions due to fossil fuel consumption are well recognized as a major contributor to climate change. In the debate on dealing with this threat, expectations are high that agriculture based economies of the developing world can help alleviate this problem. But, the contribution of agricultural operations to these emissions is fairly small. It is the clearing of native ecosystems for agricultural use in the tropics that is the largest non-fossil fuel source of CO₂ input to the atmosphere. Our calculation show that the use of fossil energy and the concomitant emission of CO₂ in the agricultural operational sector - i.e. the use of farm machinery, irrigation, fertilization and chemical pesticides - amounts to merely 3.9% of the commercial energy use in that part of the world. Of this, 70% is associated with the production and use of chemical fertilizers. In the absence of fertilizer use, the developing world would have converted even more land for cultivation, most of which is completely unsuitable for cultivation. Current expectations are that reforestation in these countries can sequester large quantities of carbon in order to mitigate excessive emissions elsewhere. But, any program that aims to set aside land for the purpose of sequestering carbon must do so without threatening food security in the region. The sole option to liberate the necessary land for carbon sequestration would be the intensification of agricultural production on some of the better lands by increased fertilizer inputs. As our calculations show, the sequestration of carbon far outweighs the emissions that are associated with the production of the extra fertilizer needed. Increasing the fertilizer use in the developing world (without China) by 20%, we calculated an overall net benefit in the carbon budget of between 80 and 206 Mt yr^?1 dependent on the carbon sequestration rate assumed for the regrowing forest. In those regions, where current fertilizer use is low, the relative benefits are the highest as responding yield increases are highest and thus more land can be set aside without harming food security. In Sub-Saharan Africa a 20% fertilizer increase, which amounts to 0.14 Mt of extra fertilizer, can tie up somewhere between 8 and 19 Mt of CO₂ per year (average: 96 t CO₂ per 1 t fertilizer). In the Near East and North Africa with a 20%-increased fertilizer use of 0.4 Mt yr^-1 between 10 and 24 Mt of CO₂ could be sequestered on the land set aside (40 t CO₂ per 1 t fertilizer). In South Asia this is 22–61 Mt CO₂ yr?1 with an annual additional input of 2.15 Mt fertilizer (19 t CO₂ per 1 t fertilizer). In fact, carbon credits may be the only way for some of the farmers in these regions to afford the costly inputs. Additionally, in regions with already relatively high fertilizer inputs such as in South Asia, an efficient use of the extra fertilizer must be warranted. Nevertheless, the net CO₂ benefit through implementation of this measure in the developing world is insignificant compared to the worldwide CO₂ output by human activity. Thus, reforestation is only one mitigating measure and not the solution to unconstrained fossil fuel CO₂ emissions. Carbon emissions should, therefore, first of all be reduced by the avoidance of deforestation in the developing world and moreover by higher energy efficiency and the use of alternative energy sources.     

Effect of hydrogen addition to CNG in a biodiesel-operated dual-fuel engine

Alternative fuels for diesel engine applications are gaining more prominence as they have numerous advantages compared to fossil fuels. They are renewable, biodegradable; provide food and energy security and foreign exchange savings. They address environmental concerns and socio-economic issues as well. Gaseous fuels such as compressed natural gas and hydrogenated compressed natural gas (HCNG) appear more attractive fuels for diesel engine applications operated in dual-fuel mode. Such dual fuel engines can replace considerable amount of liquid-injected pilot fuels by gaseous fuels besides being friendly to the environment. A small quantity of liquid fuel injected towards the end of the compression stroke initiates combustion of the inducted gas in the dual-fuel engines. The main advantage of dual-fuel engines is their lower nitrogen oxides (NO_x) and particulate emissions. Hence renewable fuels such as biodiesels and gaseous fuels can be used predominantly for transportation and power generation applications. Gaseous fuels are clean burning and are more economical as well. A suitable carburettor was designed to supply a stoichiometric mixture of air and HCNG to the modified diesel engine operated in dual-fuel mode. The biodiesel used in this study is derived from Honge oil called the Honge oil methyl ester (HOME). This paper presents the performance, combustion and exhaust emission characteristics of a single cylinder, four stroke, direct injection, stationary diesel engine operated on HOME and HCNG in dual-fuel mode. From the results it is observed that HOME–HCNG combination gave lower brake thermal efficiency (BTE) and improved emission levels when compared with diesel/HOME in single fuel operation. Lower smoke and particulate matter were obtained with dual-fuel operation. Comparative measures of BTE, peak pressure, pressure–crank angle variation, smoke opacity, hydrocarbon, carbon monoxide and NO_x emissions have been made and analysed.     

Ethanol From Corn: Clean Renewable Fuel for the Future,or Drain on Our Resources and Pockets?

It is shown here that one burns 1 gallon of gasoline equivalent in fossil fuels to produce 1 gallon of gasoline equivalent as ethanol from corn. When this corn ethanol is burned as a gasoline additive or fuel, its use amounts to burning the same amount of fuel twice to drive a car once. Therefore, the fuel efficiency of those cars that burn corn ethanol is halved. The widespread use of corn ethanol will cause manifold damage to air, surface water, soil and aquifers. The overall energy balance of corn conversion to ethanol demonstrates that 65% of the input energy is lost during the conversion. Carbon dioxide sequestration by corn is nullified when corn ethanol is burned, and there will be additional carbon dioxide, nitrous oxides, and sulfur oxide emissions from the fossil fuels used to produce the ethanol. Students in the Spring 2003 CE24 Freshman Seminar offered at U.C. Berkeley by the Civil and Environmental Engineering Department Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

The Suess effect: Carbon-Carbon interrelations

The Suess Effect is a term which has come to signify the decrease in ¹⁴C in atmospheric CO₂ owing to admixture of CO₂ produced by the combustion of fossil fuels. This term is here extended, as a concept, to the shifts in isotopic ratio of both ¹³C and ¹⁴C in any reservoir of the carbon cycle owing to anthropogenic activities. To explain this generalized Suess Effect a four reservoir global model of the natural carbon cycle is developed in which isotopic fractionation and radioactive decay are fully taken into account. The model includes the cases in which the deep ocean is treated either as a single undifferentiated box model reservoir or is vertically differentiated with eddy diffusion governing the transport of carbon. Also, the governing equations are expressed with sufficient generality to apply simultaneously to both rare isotopes. In so far as possible, the model is expressed without approximation of the isotopic processes even though this leads to non-linear differential equations to describe the rates of change of rare isotopic carbon within carbon reservoirs. Linear approximations also developed and solved using the method of Laplace transforms. The sensitivity of the predicted Suess Effects to uncertainties in the assigned values of the model parameters is investigated in detail, including estimates of some of the effects of linearizing the governing equations.The approximation of Stuiver, in which the atmospheric Suess Effect is assumed to be 0.018 times the corresponding effect for ¹⁴C, is examined in detail and shown to arise when both isotopic fractionation and radioactive decay are left out of the model. This approximation, although correct as to order of magnitude, is found to be too imprecise to be recommended in modeling studies.As found in previous work, the predicted atmospheric Suess Effect for ¹³C for a given airborne fraction of industrial CO₂ is of similar magnitude whether the land biosphere has been a net source or sink of carbon during recent times. On the other hand, the corresponding effect for a surface ocean water is considerably smaller than otherwise if the land biosphere has been a source of CO₂ instead of a sink. The model is thus useful in indicating the need to consider isotopes in several reservoirs simultaneously.Although the emphasis is on formulating models rather than surveying and interpreting data, observational data are summarized and compared with model predictions. The oceanic data are seen to be too meager as yet to help settle the question of biospheric response to man's activities.     

Energy and economic impacts of an international multi-regional carbon market

The establishment of a global multi-regional carbon market is considered to be a cost effective approach to facilitate global emission abatement and has been widely concerned.The ongoing planned linkage between the European Union’s carbon market and a new emission trading system in Australia in 2015 would be an important attempt to the practice of building up an international carbon market across different regions.To understand the abatement effect of such a global carbon market and to study its energy and economic impact on different market participants,this article adopts a global dynamic computable general equilibrium model with a detailed representation of the interactions between energy and economic systems.Our model includes 20 economic sectors and 19 regions,and describes in detail 17 energy technologies.Bundled with fossil fuel consumptions,the emission permits are considered to be essential inputs in each of the production and consumption activities in the economic system to simulate global carbon market policies.Carbon emission permits are endogenously set in the model,and can be traded between sectors and regions.Considering the current development of the global carbon market,this study takes 2020 as the study period.Four scenarios(reference scenario,independent carbon market scenario,Europe Union（EUh-Australia scenario,and China-EU-Australia scenario） are designed to evaluate the impact of the global carbon market involving China,the EU,and Australia.We find that the carbon price in the three countries varies a lot,from $32/tCO₂ in Australia,to $17.5/tCO₂ in the EU,and to $10/tCO₂ in China.Though the relative emission reduction（3%） in China is lower than that in the EU（9%） and Australia（18%）,the absolute emission reduction in China is far greater than that in the EU and Australia.When China is included in the carbon market,which already includes the EU and Australia,the prevailing global carbon price falls from $22 per ton carbon dioxide（CO₂） to $12/tCO₂,due to the relatively lower abatement cost in China.Seventy-one percent of the EU’s and eighty-one percent of Australia’s domestic reduction burden would be transferred to China,increasing 0.03%of the EU’s and 0.06%of Australia’s welfare.The emission constraint improves the energy efficiency of China’s industry sector by 1.4%,reduces coal consumption by3.3%,and increases clean energy by 3.5%.     

Life improvement programme of producer gas–biodiesel operated dual fuel engines

Biomass fuels have attracted an increase in interest due to the alarming rise in global greenhouse gases and the rapid rise of petroleum prices. Energy security on a sustainable basis can come only with the responsible use of home-sourced resources and not from imported fossil fuels such as coal or crude petroleum products. Partial combustion of biomass in the downdraft gasifier generates producer gas that can be used as the sole fuel or as a supplementary fuel for internal combustion engines. A dual fuel mode of operation, in which producer gas is used as a supplementary inducted fuel along with injected pilot fuels of Honge or Jatropha biodiesels, can be a promising alternative to diesel only usage. Two different carburettors were designed and fabricated to facilitate gas entry at 45° and 90° to the engine cylinder. The engine was experimentally optimised using Honge or Jatropha biodiesels–producer gas combinations with respect to maximum pilot fuel savings in the dual fuel mode operation, optimum air and gas mixing with different tested carburettors. The performance, combustion and emission characteristics of these dual fuel combinations were compared at different load conditions. The results showed that biodiesels of Honge or Jatropha oils–Producer gas combinations with carburettor of 90° gas entry resulted in better performance.     

Contribution of the sugar cane industry to reduce carbon dioxide emissions in the energy sector: the case of Mauritius

The aim of this paper was to present the contribution of the sugar cane industry to reduce carbon dioxide emissions in the energy sector. Mauritius is taken as a case study. Sugar cane was introduced in Mauritius during the seventeenth century and production of sugar started around 60 years later. Since then, the cane industry has been one of the economic pillars of the country. Bagasse, a by-product of sugar cane, is used as fuel in cogeneration power plants to produce process heat and electricity. This process heat and the generated electricity are used by an annexed sugar mills for the production of sugar, while the remaining electricity is exported to the national grid. In fact, Mauritius is a pioneer in the field of bagasse-based cogeneration power plant; the first bagasse-based cogeneration power plant that was commissioned in the world was in Mauritius in 1957. The contribution of the cane industry in the electricity sector has been vital for the economic development of Mauritius and also in terms of mitigating carbon dioxide emissions by displacing fossil fuels in electricity generation, as bagasse is classified as a renewable source. Data obtained from Statistics Mauritius on electricity production for the past 45 years were analysed, and carbon dioxide emissions were calculated based on international norms. It is estimated that savings on heavy fuel oil importation were by 1.5 million tons of oil—representing a value of 2.9 billion dollars—thus avoiding 4.5 million tons of carbon dioxide emissions. This figure can be further increased if molasses, a by-product of sugar cane juice, is used to produce bio-ethanol to be used as fuel in vehicles.     

Performance of a twin cylinder diesel engine in dual fuel mode using woody biomass producer gas

Due to energy crisis and shortage of fossil fuel, there is a growing interest in alternative fuel for internal combustion engine. Producer gas presents a very promising alternative fuel to diesel since it is a renewable and clean burning fuel having properties similar to that of diesel. In this study, a twin cylinder dual fuel diesel engine is experimentally optimized for maximum diesel saving and lower emissions, without any undue vibration of engine using woody biomass producer gas. The test is carried out to study the performance and emission parameters of the engine in diesel mode and dual fuel mode at different gas flow rates under different load conditions. The study reveals that maximum diesel savings is found to be 83% at optimum gas flow rate and 8 kW load. Carbon monoxide, hydrocarbon and carbon dioxide emissions in dual fuel mode were higher compared with diesel mode at all test ranges. However, the main pollutants, such as nitrogen oxide and smoke, decrease substantially in the dual fuel mode compared with the diesel mode. Lower brake thermal efficiency and higher brake-specific energy consumption as well as exhaust gas temperature are observed in dual fuel mode compared with diesel mode.     

Indoor air quality and minimum ventilation rate

In a 30-m³ test chamber the air pollutants caused by man were measured. Variables were the number of persons and the rate of air change. During 2-h test sessions the temperature, relative humidity, carbon dioxide, and intensity of odors were measured. The relationship between the perceived odor intensities and the concentrations of carbon dioxide-independent of the number of persons and the air change rate—was observed. At air change rates of 12–15 m³/person/h, the carbon dioxide concentration was not higher than 0.15% and the odor intensity was evaluated only as a “slight annoyance.” Higher ventilation rates are necessary if smoking and increased physical activities are done in the rooms.     

Energy analysis for onsite and offsite suburban wastewater

The environmental consequence of meeting the planet’s energy requirements has shown that biological degradation of organic constituent from wastewater does not only produces biogas. It also produces flammable methane that has 21 times more global warming potential or greenhouse effect than carbon dioxide. This becomes a loss of potential renewable energy when it is flared. This study investigates recoverable energy from cassava wastewater and effect of unrecovered onsite (not from treatment plant) wastewater energy. Sludge from both onsite untreated and offsite treated wastewater from a cassava processing station in a sub urban community of Nigeria was analyzed. The result shows that the offsite treatment has a methane potential of 27.428 m³/day compared to the onsite methane emission potential with 17.807 m³/day. The onsite 17.807 m³/day of methane is equivalent to 0.126 kgCH₄/year of emitted methane base on industrial procedure standards by the IPCC (2006) guidelines for national greenhouse gas inventories. An additional 54.03% of methane will be recovered if the onsite emissions were to be captured . At an emission efficiency of 0.025 kgCH₄/kg COD, the untreated wastewater indicates a potential contribution to the greenhouse effect. A mathematical model analysis was presented for ease in determining the amount of methane emitted from the untreated wastewater. This study support suggested methodologies and previous work comparing anaerobic offsite methane potential and untreated wastewater methane emission potentials along with its greenhouse effects.     

Movement towards a low carbon emitted environment: a test of some factors in Malaysia

There exists a high global concern in different nations on environmental sustainability especially at the focal stage of increased economic growth and development process due to high level of environmental degradation and pollution. The major aim of this study was to empirically examine how to minimise carbon emissions (CO₂) in Malaysia which are mainly caused by energy production, fossil fuel consumption, population density and economic growth. The study adopted the method of autoregressive distributed lag bound testing approach to analyse the data for the period 1971–2011. The study found that economic growth in Malaysia has a direct relationship with CO₂ emissions in both the short run and the long run. Similarly, there is a positive relationship between fossil fuel consumption and CO₂ emissions over the same period. Population density was found to have positive impacts on CO₂ emissions. Contrarily, the relationship between the activities of energy production and pollution is negative in the long run. The study recommends that a targeted GDP growth rate should be set with the consideration to avoid more environmental pollution. In addition, the positive impact of fossil fuel consumption on the environmental pollution implies that there is a need to make and implement policies that will encourage the use of public transportation system more than private transportations. That is, the unnecessary use of private vehicles should be discouraged in order to reduce the extent of fossil fuel consumption.     

Carbon isotopes and sulphur contents as indicators of atmospheric pollution from burning fossil fuels

This paper summarized the study carried out in Krakow, Poland in 1975-76 on the estimated local air pollution as measured by carbon isotopes and total sulphur measurement in plants. Good correlation was found between δ¹⁴C value and the total sulphur (measured by radionuclide excited X-ray fluorescence) in beech leaves collected in the late summer, indicating the common source of both pollutants. Sampling and measurement of σ¹³C in atmospheric CO₂ has shown that σ³C can be used as a pollution indicator only in the winter period when no fluctuations exist ddue to plant respiration. A method of CO₂ sampling using molecular sieve proved to be feasible for instantaneous sampling with no isotope fractionation. The highest pollution by fossil CO₂ was measured in winter (12.8% excess. During spring and summer the average contribution of fossil CO₂ was 4.5 to 5.6%.     

Can forest policy contribute to solving the CO2 problem?

The steady rise of atmospheric carbon dioxide concentration is due to the combined effects of fossil fuel burning and large scale deforestation. World-wide large scale reforestation could provide, within 15–20 years, an additional biospheric sink of the order of magnitude of the present input. Its capacity would be limited to a time span of several decades, but this time could be used to develop and deploy altenative energy sources (solar, geothermal and others) which presently are unavailable for immediate large scale use.     

Honge oil methyl ester and producer gas-fuelled dual-fuel engine operated with varying compression ratios

Alternative and renewable fuels have numerous advantages compared with fossil fuels as they are renewable and biodegradable, besides providing food and energy security and foreign exchange savings and addressing environmental and socio-economic issues. Therefore, these renewable fuels can be used predominantly in compression ignition (CI) engines for transportation purposes and power generation applications. Today, the use of biomass-derived producer gas is more relevant for addressing rural power generation and is also a promising technique for controlling both NO_x and soot emission levels. Although a producer gas–biodiesel-operated dual-fuel diesel engine exhibits lower performance, they are independent from the use of fossil fuels. The lower performance of the engine could be due to the slow-burning and lower calorific value of producer gas. For this purpose, exhaustive experiments on the use of Honge oil methyl ester (HOME)–producer gas in a dual-fuel CI engine were carried out for the improvement of its fuel efficiency. This paper presents the effect of the compression ratio (CR) on the performance, combustion and exhaust emission characteristics of a single-cylinder, four-stroke, direct injection stationary diesel engine operated using HOME and producer gas in a dual-fuel mode. The results indicated that the HOME–producer gas combination exhibited lower brake thermal efficiency (BTE) with comparable emission levels with the diesel–producer gas combination at different CRs. Comparative measures of BTE, peak pressure, pressure–crank angle variation, heat release rate, smoke opacity, and hydrocarbon (HC), carbon monoxide (CO) and nitric oxide (NO_x) emission levels are presented and analysed.     

Man-made and natural smog in California

The radiocarbon content in creosote bush in the greater Los Angeles area has been found to reflect the distribution of smog. Indications are that smog in the even larger air basin of the San Joaquin Valley of California may be caused in part by recent biospheric emissions rather than by fossil fuel combustion alone.