Design considerations and economics of different shaped surface aeration tanks

This paper deals with the design considerations of surface aeration tanks on two basic issues of oxygen transfer coefficient and power requirements for the surface aeration system. Earlier developed simulation equations for simulating the oxygen transfer coefficient with theoretical power per unit volume have been verified by conducting experiments in geometrically similar but differently shaped and sized square tanks, rectangular tanks of length to width ratio (L/W) of 1.5 and 2 as well as circular tanks. Based on the experimental investigations, new simulation criteria to simulate actual power per unit volume have been proposed. Based on such design considerations, it has been demonstrated that it is economical (in terms of energy saving) to use smaller tanks rather than using a bigger tank to aerate the same volume of water for any shape of tanks. Among the various shapes studied, it has been found that circular tanks are more energy efficient than any other shape.

Potential and economics of forestry options for carbon sequestration in India

There is a need to understand the carbon (C) sequestration potential of the forestry option and its financial implications for each country.In India the C emissions from deforestation are estimated to be nearly offset by C sequestration in forests under succession and tree plantations. India has nearly succeeded in stabilizing the area under forests and has adequate forest conservation strategies. Biomass demands for softwood, hardwood and firewood are estimated to double or treble by the year 2020. A set of forestry options were developed to meet the projected biomass needs, and keeping in mind the features of land categories available, three scenarios were developed: potential; demand-driven; and programme-driven scenarios. Adoption of the demand-driven scenario, targeted at meeting the projected biomass needs, is estimated to sequester 78 Mt of C annually after accounting for all emissions resulting from clearfelling and end use of biomass. The demand-driven scenario is estimated to offset 50% of national C emission at 1990 level. The cost per t of C sequestered for forestry options is lower than the energy options considered. The annual investment required for implementing the demand-driven scenario is estimated to be US$ 2.1 billion for six years and is shown to be feasible. Among forestry options, the ranking based on investment cost per t of C sequestered from least cost to highest cost is; natural regeneration-agro-forestry-enhanced natural regeneration (< US$ 2.5/t C)-timber-community-softwood forestry (US$ 3.3 to 7.3 per t of C).

Rejection of technology

It is well accepted that technology plays a critical role in socio-technical transitions, and sustainable development pathways. A society‘s amenability to the intervening (sustainable) technology is fundamental to permit these transitions. The current age is at a juncture wherein technological advancements and capacities provide the common individual with affordable and unlimited choice. Technological advancement and complexity can either remain simple and unseen to the user or may daunt him to keep away, in which case the intended pathways remain unexploited. The current paper explores the reasons behind rejection of technology and proposes a solution model to address these factors in accommodating socio-technical transitions. The paper begins with structuring the societal levels at which technological rejection occurs and proceeds to discuss technology rejection at the individual user (niche)level. The factors influencing decisions regarding technology rejection are identified and discussed with particular relevance to the progressive world (Asia).