THE ECONOMICS OF RENEWABLE ENERGY SYSTEMS FOR DEVELOPING COUNTRIES

In many parts of the Third World, projects are being developed to test such renewable energy systems as biogas plants and solar cell arrays for powering pumps and grinders. Virtually nowhere, however, has adequate work been done to determine if these systems are worth their costs. This paper outlines the cost-benefit techniques which allow systems to be evaluated from the standpoint of individual buyers (financial analysis) and the society as a whole (economic analysis). Special attention is given to problems of particular importance in reviewing energy systems, including local measurement of costs and benefits, determination of investors' discount rates, shadow-pricing and allowance for social costs. Detailed cost-benefit analyses are provided for two representative systems: a family-scale Indian biogas plant and a 5.5 kW solar cell irrigation pump on the borders of Lake Chad. The family-scale biogas plant does not appear to be profitable in either financial or economic terms under any plausible sets of assumptions. The solar cell pump has positive net benefits by economic (if not financial) measures, but is unlikely soon to be competitive with diesel power for most applications. At best, some of these devices might ultimately become competitive with expensive commercial energy. Such devices will therefore be of interest first to people now using substantial amounts of such energy – that is, the relatively wealthy. Only much later might significant benefits begin to filter down to the poor. In the light of these findings renewed attention should be given to meeting basic energy needs through less sophisticated systems. By finding systems whose benefits are commensurate with their costs, and whose costs are within reach of the poor, it may be possible to provide more energy to those most in need of it. Dans de nombreuses parties du Tiers Monde, des projets sont en cours d'exécution en vue d'évaluer des systèmes en matière d'énergie de remplacement, tels que des usines de gaz de fermentation et des assemblages de cellules solaires pour activer pompes et broyeurs. Toutefois, il semblerait qu'il n'y ait eu nulle part aucune étude valable permettant de déterminer si ces systèmes justifient leur coût. Cet article relève les techniques de coût-utilité qui permettent d'évaluer ces systèmes du point de vue des acheteurs individuels (analyse financière) et de la société dans son ensemble (analyse économique). En analysant ces systèmes, l'article souligne des problèmes d'importance particulière, y compris l'évaluation locale des coûts et profits, la détermination des taux d'actualisation d'investissement, l'estimation des prix virtuels et l'établissement de marges de coûts sociaux. Des analyses détaillées de coût-utilité sont présentées pour deux systèmes concrets: une usine de gaz de fermentation indienne à l'échelle de la famille, et une pompe d'irrigation à cellules solaires de 5,5 kW sur les rives du lac Chad. L'usine de gaz de fermentation à l'échelle de la famille ne semble ni financièrement, ni économiquement rentable quelque soient les termes plausibles des hypothèses. La pompe à cellules solaires offre des profits positifs nets selon des critères économiques (sinon financiers) mais, dans la plupart des cas, elle ne semble pas pouvoir concurrencer le moteur diesel dans un proche avenir. Au mieux, quelques-unes de ces installations peuvent à la longue concurrencer l'énergie commerciale à prix élevé. Par conséquent, elles seront d'intérêt particulier tout premièrement aux usagers de grande quantité de cette énergie, c'est-à-dire ceux possédant des moyens relativement élevés. Ce n'est que bien plus tard que les classes défavorisées pourront commencer à bénéficier sensiblement des profits qui en résulteront. Sur la base de ces données, les organisations s'intéressant aux classes défavorisées peuvent se pencher à nouveau sur la manière de répondre aux besoins essentiels en matière d'énergie en utilisant des systèmes plus simples: bois appartenant aux villages, fours à bois améliorés, pompes et broyeurs à pédales ou à bras, pompes foulantes hydrauliques, etc. En conçevant des systèmes dont les profits sont proportionnels aux coûts et dont les coûts sont à la portée des classes défavorisées, il se peut que l'on puisse mettre plus d'énergie à la disposition de ceux qui en ont le plus besoin. En muchas partes del Tercer Mundo se han llevado a cabo proyectos para ensayar sistemas de energía renovables tales como plantas de biogas, y celdas solares para operar bombas y molinos. Sin embargo practicamente en ninguna parte se ha hecho el esfuerzo apropiado para determinar si estos sistemas valen lo que cuestan. Este artículo esboza las técnicas de beneficio-costo para evaluar dichos sistemas desde el punto de vista del usuario individual (análisis financiero) y del de la sociedad como un todo (análisis económico). Se da especial atención a los problemas de importancia particular en el análisis de sistemas de energía, incluyendo mediciónes locales de costos y beneficios, determinación de la tasa de descuento del inversionista, precios-sombra y costos sociales. Detallados análisis de beneficio-costo se proveen para dos sistemas representativos: una planta de biogas en escala familiar y una bomba de agua operada por celadas solares de 5.5 kW al borde del Lago Chad. La planta de biogas a escala familiar parece no ser rentable financieramente ni económicamente bajo ninguna serie de hipótesis realistas. La bomba de celdas solares tiene un benefico económico positivo (aunque no financiero), pero es poco provable que sea competitivo con el motor diesel para la mayoría de las aplicaciones. En el mejor de los casos, alguno de estos sistemas pueden ser competitivos con una energía comercial cara. Estos sistemas en consecuencia serán de gran interés primeramente para las personas que hacen uso intensivo de energía, esto es, las personas relativamente adineradas. Pueda qui solo mucho despues beneficios significativos lleguen a los pobres. A la luz de estos resultados debe ponerse renovada atención a satisfacer las necesidades básicas de energía a través de sistemas menos sofisticados. Pueda que sea posible proveer mas energía a los que más necesitan de ella si se buscan sistemas cuyo beneficios sea proporcionados a sus costos y que dichos costos esten al alcance de los pobres.     

Early Secondary Succession in Bottomland Hardwood Forests of Southeastern Virginia

Addressing the need for reference sites that permit wetland managers to evaluate the relative success of wetland restoration efforts, this project examines the early successional properties of a chronosequence of 17 forested wetlands that have been clear-cut and allowed to naturally revegetate. Ordinations performed on the data using CANOCO software indicated three general types of communities—one dominated by bald cypress (Taxodium distichum) and water tupelo (Nyssa aquatica), one dominated by black willow (Salix nigra), and one with a species composition similar to that of a mature stand of bottomland hardwoods. These divisions were correlated with the percentage of stems originating as coppice on stumps leftover from the clear-cut. In particular, the bottomland hardwood stands were regenerating predominantly as coppice, while the cypress/tupelo and black willow stands were regenerating primarily as seedlings. As indicated by the earlier development of overstory basal area, coppice sites were also regenerating much faster. The hydrology of a site also exhibited a strong impact on the rate of regeneration, with the semipermanently to permanently flooded portions of sites often exhibiting little or no regeneration. The results indicate that, because of the overwhelming reliance on coppice sprouts as the main source of stems and the concomitant enhanced rates of regeneration, certain vegetative parameters of clear-cut bottomland hardwood stands would not be effective benchmarks by which to judge the relative success of creation and restoration efforts.     

Physiological and Morphological Response Patterns of <Emphasis Type="Italic">Populus deltoides</Emphasis> to Alluvial Groundwater Pumping

We examined the physiological and morphological response patterns of plains cottonwood [Populus deltoides subsp. monilifera (Aiton) Eck.] to acute water stress imposed by groundwater pumping. Between 3 and 27 July 1996, four large pumps were used to withdraw alluvial groundwater from a cottonwood forest along the South Platte River, near Denver, Colorado, USA. The study was designed as a stand-level, split-plot experiment with factorial treatments including two soil types (a gravel soil and a loam topsoil over gravel), two water table drawdown depths (∼0.5 m and >1.0 m), and one water table control (no drawdown) per soil type. Measurements of water table depth, soil water potential (Ψ_s), predawn and midday shoot water potential (Ψ_pd and Ψ_md), and D/H (deuterium/hydrogen) ratios of different water sources were made in each of six 600-m² plots prior to, during, and immediately following pumping. Two additional plots were established and measured to examine the extent to which surface irrigation could be used to mitigate the effects of deep drawdown on P. deltoides for each soil type. Recovery of tree water status following pumping was evaluated by measuring stomatal conductance (g _s ) and xylem water potential (Ψ_xp) on approximately hourly time steps from before dawn to mid-afternoon on 11 August 1996 in watered and unwatered, deep-drawdown plots on gravel soils. P. deltoides responded to abrupt alluvial water table decline with decreased shoot water potential followed by leaf mortality. Ψ_pd and percent leaf loss were significantly related to the magnitude of water table declines. The onset and course of these responses were influenced by short-term variability in surface and ground water levels, acting in concert with physiological and morphological adjustments. Decreases in Ψ_pd corresponded with increases in Ψ_md, suggesting shoot water status improved in response to stomatal closure and crown dieback. Crown dieback caused by xylem cavitation likely occurred when Ψ_pd reached −0.4 to −0.8 MPa. The application of surface irrigation allowed trees to maintain favorable water status with little or no apparent cavitation, even in deep-drawdown plots. Two weeks after the partial canopy dieback and cessation of pumping, g _s and Ψ_xp measurements indicated that water stress persisted in unwatered P. deltoides in deep-drawdown plots.     

Influence of Agricultural Antibiotics and 17β-Estradiol on the Microbial Community of Soil

Agricultural pharmaceuticals are a major environmental concern because of their hazardous effects on human and wildlife. This study analyzed phospholipid ester-linked fatty acids (PLFAs) and quinones to investigate the effects of a steroid (17β-estradiol) and agricultural antibiotics (chlortetracycline and tylosin) on soil microbes in the laboratory. Two different types of soil were used: Sequatchie loam (0.8% organic matter) and LaDelle silt loam (9.2% organic matter). The soils were spiked with 17β-estradiol and antibiotics, alone or in combination. In Sequatchie loam, 17β-estradiol significantly increased the microbial biomass, especially the biomarkers for beta proteobacteria (16:1ω7c, 18:1ω7c, Cy17:0, and UQ-8). The coexistence of antibiotics decreased the stimulatory effect of 17β-estradiol on the microbial community. In LaDelle silt loam, there were no significant differences in total microbial biomass and their microbial community structure among the treatments. Overall, 17β-estradiol changed the microbial community of soil and the presence of antibiotics nullified the effect of 17β-estradiol. However, the effects of 17β-estradiol and antibiotics on soil microbes were sensitive to the soil properties, as seen in the LaDelle silt loam.     

Reconciling Salvage Logging of Boreal Forests with a Natural-Disturbance Management Model

Abstract:  In North American boreal forests, wildfire is the dominant agent of natural disturbance. A natural-disturbance model has therefore been promoted as an ecologically based approach to forest harvesting in these systems. Given accelerating resource demands, fire competes with harvest for timber, and there is increasing pressure to salvage naturally burned areas. This creates a management paradox: simultaneous promotion of natural disturbance as a guide to sustainability while salvaging forests that have been naturally disturbed. The major drivers of postfire salvage in Canadian boreal forests are societal perceptions, overallocation of forest resources, and economic and policy incentives, and postfire salvage compromises forest sustainability by diminishing the role of fire as a critical, natural process. These factors might be reconciled through consideration of fire in resource allocations and application of active adaptive management. We provide novel treatment of the role of burn severity in mediating biotic response by examining its influence on the amount, type, and distribution of live, postfire residual material, and we highlight the role of fire in shaping spatial and temporal patterns in forest biodiversity. Maintenance of natural postfire forests is a critical component of an ecosystem-based approach to forest management in boreal systems. Nevertheless, present practices focus heavily on expediting removal of timber from burned forests, despite increasing evidence that postfire communities differ markedly from postharvest systems, and there is a mismatch between emerging management models and past management practices. Policies that recognize the critical role of fire in these systems and facilitate enhanced understanding of natural system dynamics in support of development of sustainable management practices are urgently needed.     

Appreciating Ecological Complexity: Habitat Contours as a Conceptual Landscape Model

Abstract:  Organisms respond to their surroundings at multiple spatial scales, and different organisms respond differently to the same environment. Existing landscape models, such as the "fragmentation model" (or patch-matrix-corridor model) and the "variegation model," can be limited in their ability to explain complex patterns for different species and across multiple scales. An alternative approach is to conceptualize landscapes as overlaid species-specific habitat contour maps. Key characteristics of this approach are that different species may respond differently to the same environmental conditions and at different spatial scales. Although similar approaches are being used in ecological modeling, there is much room for habitat contours as a useful conceptual tool. By providing an alternative view of landscapes, a contour model may stimulate more field investigations stratified on the basis of ecological variables other than human-defined patches and patch boundaries. A conceptual model of habitat contours may also help to communicate ecological complexity to land managers. Finally, by incorporating additional ecological complexity, a conceptual model based on habitat contours may help to bridge the perceived gap between pattern and process in landscape ecology. Habitat contours do not preclude the use of existing landscape models and should be seen as a complementary approach most suited to heterogeneous human-modified landscapes.     

Pyric Herbivory: Rewilding Landscapes through the Recoupling of Fire and Grazing

Abstract:  Our understanding of fire and grazing is largely based on small-scale experimental studies in which treatments are uniformly applied to experimental units that are considered homogenous. Any discussion of an interaction between fire and grazing is usually based on a statistical approach that ignores the spatial and temporal interactions on complex landscapes. We propose a new focus on the ecological interaction of fire and grazing in which each disturbance is spatially and temporally dependent on the other and results in a landscape where disturbance is best described as a shifting mosaic (a landscape with patches that vary with time since disturbance) that is critical to ecological structure and function of many ecosystems. We call this spatiotemporal interaction pyric herbivory (literal interpretation means grazing driven by fire). Pyric herbivory is the spatial and temporal interaction of fire and grazing, where positive and negative feedbacks promote a shifting pattern of disturbance across the landscape. We present data we collected from the Tallgrass Prairie Preserve in the southern Great Plains of North America that demonstrates that the interaction between free-roaming bison ( Bison bison ) and random fires promotes heterogeneity and provides the foundation for biological diversity and ecosystem function of North American and African grasslands. This study is different from other studies of fire and grazing because the fires we examined were random and grazing animals were free to roam and select from burned and unburned patches. For ecosystems across the globe with a long history of fire and grazing, pyric herbivory with any grazing herbivore is likely more effective at restoring evolutionary disturbance patterns than a focus on restoring any large vertebrate while ignoring the interaction with fire and other disturbances .     

Predicting Risk of Habitat Conversion in Native Temperate Grasslands

Abstract: Native grasslands that support diverse populations of birds are being converted to cropland at an increasing rate in the Prairie Pothole Region of North America. Although limited funding is currently available to mitigate losses, accurate predictions of probability of conversion would increase the efficiency of conservation measures. We studied conversion of native grassland to cropland in the Missouri Coteau region of North and South Dakota (U.S.A.) during 1989–2003. We estimated the probability of conversion of native grassland to cropland with satellite imagery and logistic regression models that predicted risk of conversion and by comparing the overlap between areas of high biological value and areas most vulnerable to conversion. Annualized probability of conversion was 0.004, and 36,540 ha of native grassland were converted to cropland during the period of our study. Our predictive models fit the data and correctly predicted 70% of observed conversions of grassland. Probability of conversion varied spatially and was correlated with landscape features like amount of surrounding grassland, slope, and soil productivity. Tracts of high biological value were not always at high risk of conversion. We concluded the most biologically valuable areas that are most vulnerable to conversion should be prioritized for conservation. This approach can be applied broadly to other systems and offers great utility for implementing conservation in areas with spatially variable biological value and probability of conversion.