Principal Greenhouse Gas Research Articles

Bioethanol production: Status and prospects

Production of fuel ethanol from renewable lignocellulosic materials (“bioethanol”) has the potential to reduce burgeoning world dependence on petroleum while decreasing net emissions of carbon dioxide, the principal greenhouse gas. This paper reviews the benefits and status of bioethanol production technology, focusing mostly on recent developments in the United States of America. The composition of representative lignocellulosic biomass species is presented and processing options under investigation are described. Discussion of current research directions highlights recent breakthroughs that significantly improve the prospects for commercialization. The pace of recent developments suggests that large-scale bioethanol production facilities will come on line in the United States within the next several years.

Asia-Wide Emissions of Greenhouse Gases

Emissions of principal greenhouse gases (GHGs) from Asia are increasing faster than those from any other continent. This is a result of rapid economic growth, as well as the fact that almost half of the world's population lives in Asian countries. In this paper, we provide estimates of emissions of the two principal greenhouse gases, carbon dioxide (C02) and methane (CH4), from individual countries and areas. Recent literature has been reviewed for emission estimates for individual sources, such as carbon dioxide from cement manufacture, and methane from rice fields. There are very large uncertainties in many of these estimates, so several estimates are provided, where available. The largest anthropogenic source of CO2 emissions is the use of fossil fuels. Energy consumption data from 1992 have been used to calculate estimated emissions of CO2 from this source. In view of the ongoing negotiations to limit future greenhouse gas emissions, estimates of projected CO2 emissions from the developing countries of Asia are also provided. These are likely to be 3 times their 1986 levels by 2010, under “business as usual” scenarios. Even with the implementation of energy efficiency measures and fuel switching where feasible, the emissions of CO2 are likely to double within the same time period.

Sustainable systems of intensive livestock production for the humid tropics using local resources

AbstractThe design of sustainable intensive livestock production systems for developing countries must be judged according to their likely impact on economic, ecological, ethological and sociological issues. Economic issues to be satisfied include international competitivity in price of finished products which requires maximizing comparative advantages of available natural resources. Ecological sustainability requires that the production system will result in (i) reduced emissions of the principal greenhouse gases carbon dioxide and methane; (ii) reduced contamination of soil and water resources; (iii) an effective control of soil erosion; and (iv) self sufficiency in on-farm production of energy from renewable resources. Ethological concerns relate to potential effects of production systems on animal welfare and the safety and consumer acceptability (wholesomeness) of foods produced in such systems. Sociological acceptability requires that employment opportunities are increased, especially for women, and that the production system encourages self-reliance with minimum dependence on outside inputs.The basic technology, designed and adapted by Convenio Interinstitucional para la Producción Pecuaria en el Valle del Rio Cauca (CIPAV) and cooperating local farmers in the Cauca Valley of Colombia, uses sugar cane, multipurpose trees and water plants as sources of biomass to provide food for a range of livestock species and fuel for the farm and the family. The chosen crops have a proven high capacity to fix atmospheric carbon dioxide and nitrogen into biomass, which is a permanent carbon reservoir (1 ha planted in sugar cane and trees is a sink for some 80 t carbon dioxide), and also a source of substrate for food and fuel. Sugar cane and trees help prevent erosion, maintain soil fertility, have well developed systems of biological pest control, require minimum synthetic chemical inputs and are easily separated into high and low fibre fractions as required for the different end uses of food for monogastric and ruminant animals and fuel.The preferred animal species are pigs and ducks which adapt readily to the ‘non-conventional’ high-moisture food resources (mainly cane juice, tree leaves and water plants) and have a high meat : methane production ratio. They are complemented by African sheep, dual purpose (Holsteinzebu) cattle and buffaloes, managed as triple purpose animals (draught, milk and meat) and deriving most of their food from the more nutritive parts of the fibrous crop residues. All the livestock are managed in partial or total confinement to minimize environmental damage and to maximize nutrient recycling to the crops.Fuel for the family is derived from the biodigestor which uses as substrate the excreta from the pigs; and from the sugar cane bagasse. Earthworms upgrade the fertilizer value of the excreta from the ruminant animals and produce part of the protein for the ducks.The CIPAV model is flexible as witnessed by the increasing acceptance of many of the elements in the model by both resource-poor and entrepreneurial farmers. The biomass concept, on which the CIPAV model is based, can also be scaled up to the level of agro-industry (the biomass refinery) offering renewable alternatives to present fossil-fuel-based technologies for chemical and energy needs.

Sequestration of C02 in the deep ocean by shallow injection

To alleviate the increasing atmospheric concentrations of carbon dioxide, the principal greenhouse gas, Marchetti1 proposed that CO2, might be separated from flue gases and injected into the oceans. This, and subsequent studies2–5, emphasized the need to inject the gas at great depths or in sinking currents to avoid rapid outgassing to the atmosphere. Here we show that, to the contrary, the increase in water density that results from CO2, dissolution may be sufficient to transport the dissolved gas to lower depths even for shallow injection (in the upper 200–400 m of the ocean). If the CO2 is injected near the shore, gravity currents will carry the dense, CO2-rich waters along the bottom slope towards deep water. Shallow injection near the shore will be less expensive in terms of energy and capital than deep-ocean injection. We suggest that the coast of Norway, in the vicinity of existing oil and gas fields and of planned gas power plants, provides an example of a region where the negative buoyancy of CO2-enriched sea water would transport the gas from emission sites to the deep ocean. The effect of such measures on marine life downstream of the injection point remains to be evaluated.

Global What? Control Possibilities of CO2 and Other Greenhouse Gases

Global what? is a frequent response by those who first hear of the potential for global warming, global climate change, and global catastrophe, potentially brought on by excessive greenhouse gases in the upper atmosphere. The principal greenhouse gas, CO2, is joined by methane, N2O, and other trace gases in absorbing infrared radiation, which would otherwise escape into space, a process thought to be responsible for gradual increase in temperature that will melt ice caps and raise ocean levels. This paper discusses control possibilities that could be considered once there is agreement that CO2 must be controlled. Many of the responses to the energy crisis of 1974 are applicable for CO2 control. A variety of technologies, energy sources, and ideas are offered that, in combination, could be the basis for a global energy policy. Conversion and replacement of coal, oil, and eventually natural gas fired electric power plants with other energy sources such as nuclear, solar, wind, tidal, and geothermal, could significantly reduce CO2 emissions. There are, however, no good alternatives to fossil fuels used in transportation that significantly reduce CO2 emissions. Of all the fossil fuels, natural gas has the least CO2 production. Electric vehicles and hydrogen-fueled engines are future possibilities, but the electricity for the electric cars and for making hydrogen must be from nonfossil fuel driven generators. Conservation, efficiency, and tax incentives are other parts of a control strategy, once the amount of control considered necessary is established. Renewed interest in nonfossil fuel energy sources and their research and development is obviously needed.