Making carbon sequestration a paying proposition

Atmospheric carbon dioxide (CO₂) has increased from a preindustrial concentration of about 280 ppm to about 367 ppm at present. The increase has closely followed the increase in CO₂ emissions from the use of fossil fuels. Global warming caused by increasing amounts of greenhouse gases in the atmosphere is the major environmental challenge for the 21st century. Reducing worldwide emissions of CO₂ requires multiple mitigation pathways, including reductions in energy consumption, more efficient use of available energy, the application of renewable energy sources, and sequestration. Sequestration is a major tool for managing carbon emissions. In a majority of cases CO₂ is viewed as waste to be disposed; however, with advanced technology, carbon sequestration can become a value-added proposition. There are a number of potential opportunities that render sequestration economically viable. In this study, we review these most economically promising opportunities and pathways of carbon sequestration, including reforestation, best agricultural production, housing and furniture, enhanced oil recovery, coalbed methane (CBM), and CO₂ hydrates. Many of these terrestrial and geological sequestration opportunities are expected to provide a direct economic benefit over that obtained by merely reducing the atmospheric CO₂ loading. Sequestration opportunities in 11 states of the Southeast and South Central United States are discussed. Among the most promising methods for the region include reforestation and CBM. The annual forest carbon sink in this region is estimated to be 76 Tg C/year, which would amount to an expenditure of $11.1–13.9 billion/year. Best management practices could enhance carbon sequestration by 53.9 Tg C/year, accounting for 9.3% of current total annual regional greenhouse gas emission in the next 20 years. Annual carbon storage in housing, furniture, and other wood products in 1998 was estimated to be 13.9 Tg C in the region. Other sequestration options, including the direct injection of CO₂ in deep saline aquifers, mineralization, and biomineralization, are not expected to lead to direct economic gain. More detailed studies are needed for assessing the ultimate changes to the environment and the associated indirect cost savings for carbon sequestration.     

Soil carbon sequestration in tropical agroforestry systems: a feasibility appraisal

Agroforestry is recognized as a strategy for soil carbon sequestration (SCS) under the afforestation/reforestation activities, but our understanding of soil carbon (C) dynamics under agroforestry systems (AFS) is not adequate. Although some SCS estimates are available, many of them lack scientific rigor. Several interrelated and site-specific factors ranging from agroecological conditions to system management practices influence the rate and extent of SCS under AFS, so that generalizations tend to become unrealistic. Furthermore, widely and easily adoptable methodologies are not available for estimating the SCS potential under different conditions. In spite of these, there is an increasing demand for developing “best-bet estimates” based on the current level of knowledge and experience. This document presents an attempt in that direction. The appraisal validates the conjecture that AFS can contribute to SCS, and presents indicative ranges of SCS under different AFS in the major agroecological regions of the tropics. The suggested values range from 5 to 10 kg C ha^?1 in about 25 years in extensive tree-intercropping systems of arid and semiarid lands to 100–250 kg C ha^?1 in about 10 years in species-intensive multistrata shaded perennial systems and homegardens of humid tropics.     

Soil carbon sequestration in a changing global environment

Throughout its long history the Earth has undergone warm periods with high atmospheric concentrations of greenhouse gases (GHG), and has responded with different buffering mechanisms whereby atmospheric C has been transferred to other geochemical compartments. Strategies for the mitigation and adaptation to the current climatic forcing may thus be generated by the acceleration of such natural mechanisms, especially those involved in short cycles, mainly in the biosphere and the pedosphere. Although these contain smaller C stocks than other compartments (< 0.01% of the total C), they circulate large amounts of C from the atmosphere through photosynthesis and mineral weathering (e.g., 120 Pg C are circulated through terrestrial ecosystems and total C in the atmospheric compartment is 805 Pg C). Increased C sequestration can thus be achieved in terrestrial ecosystems, by: (1) favouring growth of biomass; (2) promoting and facilitating carbonation processes; (3) reducing erosion and favouring pedogenesis; (4) developing organic matter-rich horizons; (5) recovering degraded or contaminated soils, and/or (6) managing waste by use of systems that minimize emissions of GHG. Within the latter option, the following actions are considered here in more detail: 1) production of Technosols, and 2) production of biochar. All of the above options should form part of a strategy for the mitigation and adaptation to global climate change. In this review, we analyze those focused on promoting soil conservation, soil restoration and soil formation.     

Mediterranean shrublands carbon sequestration: environmental and economic benefits

To date, only a few attempts have been done to estimate the contribution of Mediterranean ecosystems to the global carbon cycle. Within this context, shrub species, composition and structure of the Mediterranean shrublands developing along the Latium coast (Italy) were analyzed in order to evaluate their contribution to carbon (C) sequestration, also taking into consideration the economic benefits at a national level. The considered shrublands had a shrub density of 1,200?±?500 shrubs ha^?1. Shrubs were classified into small (S), medium (M) and large (L), according to their volume (V) and leaf area index (LAI). The total yearly carbon dioxide (CO₂) sequestration per species (SC_y) was calculated multiplying the total photosynthetic leaf surface area (spt) of each species by the mean yearly photosynthetic rate and the total yearly photosynthetic activity time (in hours). Q. ilex and A. unedo had the highest SC_y (46.2?±?15.8 kg CO₂ year^?1, mean value), followed by P. latifolia (17.5?±?6.2 kg CO₂ year^?1), E. arborea, E. multiflora, C. incanus, P. lentiscus, R. officinalis, and S. aspera (6.8?±?4.2 kg CO₂ year^?1, mean value). The total yearly CO₂ sequestration per shrub (SC_shy) was 149?±?5 kg CO₂ year^?1 in L, decreasing 30 % in M and 80 % in S shrubs. Taking into account the frequency of S, M and L and their SC_shy, the total CO₂ sequestration of the Mediterranean maquis was quantified in 80 Mg CO₂ ha^?1?year^?1, corresponding to 22 Mg C ha^?1?year^?1. From a monetary viewpoint, this quantity could be valued to more than 500 US$ ha^?1?year^?1. Extending this benefit to the Mediterranean shrublands throughout the whole country, we obtained a nationwide estimated annual benefit in the order of $500 million.     

Potential for carbon sequestration in Canadian forests and agroecosystems

The potential for carbon (C) sequestration was examined in selectedCanadian forest settings and prairie agroecosystems under severalmanagement scenarios. A simple C budget model was developed toquantitatively examine C sequestration potential in living biomass of forestecosystems, in associated forest-product C pools, and in displaced fossil-fuelC. A review of previous studies was conducted to examine C sequestrationpotential in prairie agroecosystems. In the forest settings examined, ourwork suggests that substantial C sequestration opportunities can be realizedin the short term through the establishment of protected forest-C reserves.Where stands can be effectively protected from natural disturbance, peaklevels of biomass C storage can exceed that under alternative managementstrategies for 200 years or more. In settings where it is not feasible tomaintain protected forest-C reserves, C sequestration opportunities can berealized through maximum sustained yield management with harvestedbiomass put towards the displacement of fossil fuels. Because there is afinite capacity for C storage in protected forest-C reserves, harvesting forestbiomass and using it to displace the use of fossil fuels, either directlythrough the production of biofuels or indirectly through the production oflong-lived forest products that displace the use of energy-intensive materialssuch as steel or concrete, can provide the greatest opportunity to mitigategreenhouse gas emissions in the long term. In Canadian prairieagroecosystems, modest C sequestration can be realized while enhancingsoil fertility and improving the efficiency of crop production. This can bedone in situations where soil organic C can be enhanced without relianceupon ongoing inputs of nitrogen fertilizer, or where the use of fossil fuelsin agriculture can be reduced. More substantial C offsets can be generatedthrough the production of dedicated energy crops to displace the use offossil fuels. Where afforestation or reconstruction of native prairieecosystems on previously cultivated land is possible, this represents thegreatest opportunity to sequester C on a per unit-area basis. However,these last two strategies involve the removal of land from crop production,and so they are not applicable on as wide a scale as some other Csequestration options which only involve modifications to currentagricultural practices.     

中国森林碳汇潜力与增汇成本评估——基于Meta分析方法

准确评估中国森林碳汇潜力与增汇成本的经济可行性,是科学制定碳中和林业行动方案的基础。然而针对中国森林碳汇潜力与增汇成本的不同结果差异明显,可靠性需要进一步验证。为此,基于相关文献,采用Meta分析方法,对中国森林碳汇潜力与增汇成本及其导致差异的原因展开评估。研究表明：(1)中国森林碳汇量呈现不断增长的态势,但不同研究对森林碳汇潜力测度结果存在较大差异。(2)中国森林增汇的平均成本为220.45元/t CO_2e(区间值为3.9～1457.02元/t CO_2e),与工业减排成本相比,中国森林增汇更具有经济可行性,但波动幅度较大。(3)评估方法采用、碳库数量选择等因素是导致已有森林碳汇潜力文献估计结果差异的关键因素;森林增汇成本差异则主要受碳汇成本测度研究方法、成本收益数据来源等因素影响。(4)中国森林增汇对碳中和的贡献将会持续增加。基于研究结果,提出进一步深化森林碳汇潜力与成本测算相关研究等方面的政策建议。     

Potential world garbage and waste carbon sequestration

To offset the carbon dioxide released by fossil fuels, a proposed sequestration strategy relies on burying garbage and waste in landfills. This paper roughly estimates the current annual world supply of carbonaceous waste to be 35.5 billion metric tons and to contain about 18 billion metric tons of carbon. If landfills received all of this waste, sequestration of more than 5.6 billion metric tons of carbon seems theoretically possible—an amount well in excess of the 3.3 billion metric tons which the atmosphere is currently gaining.     

Wood products: potential carbon sequestration and impact on net carbon emissions of industrialized countries

Carbon stocks in the wood products pool are considered to be increasing globally. Simplified methods for estimating the fate of carbon in wood products need to be prepared to allow estimation at the national level. Since current methods cause some problems when dealing with specific countries, we try to improve the current methods. We discuss the potential carbon sequestration in wood products and the impacts of three accounting approaches (IPCC default, stock-change and atmospheric-flow) on net carbon emissions of 16 industrialized countries. We draw the following conclusions: (1) we improved the current methods for estimating the fate of carbon by considering the recycling of paper and the use of other fiber pulp, but further improvement need to be made; (2) the annual carbon sequestrations in wood products during 1990–1999 correspond to a few to 10% of 1990 base-year emissions from fossil fuels and cement production, depending on country and year. For the analyzed countries as a whole, the annual carbon sequestration was around 2%; (3) the impact of the accounting approaches on net carbon emissions at the national level is significant. Therefore, policy implications must be carefully considered when one of these approaches is adopted.     

Transaction costs for carbon sequestration projects in the tropical forest sector

There is general consensus that carbon (C) sequestration projects in forests are a relatively low cost option for mitigating climate change, but most studies on the subject have assumed that transaction costs are negligible. The objectives of the study were to examine transaction costs for forest C sequestration projects and to determine the significance of the costs based on economic analyses. Here we examine four case studies of active C sequestration projects being implemented in tropical countries and developed for the C market. The results from the case studies were then used with a dynamic forest and land use economic model to investigate how transaction costs affect the efficiency and cost of forest C projects globally. In the case studies transaction costs ranged from 0.38 to 27 million US dollars ($0.09 to $7.71/t CO₂) or 0.3 to 270 % of anticipated income depending principally on the price of C and project size. The three largest cost categories were insurance (under the voluntary market; 41–89 % of total costs), monitoring (3–42 %) and regulatory approval (8–50 %). The global analysis indicated that most existing estimates of marginal costs of C sequestration are underestimated by up to 30 % because transaction costs were not included.     

The carbon sequestration potential of tree crop plantations

Carbon (C) conservation and sequestration in many developing countries needs to be accompanied by socio-economic improvements. Tree crop plantations can be a potential path for coupling climate change mitigation and economic development by providing C sequestration and supplying wood and non-wood products to meet domestic and international market requirements at the same time. Financial compensation for such plantations could potentially be covered by the Clean Development Mechanism under the United Nations Framework Convention on Climate Change (FCCC) Kyoto Protocol, but its suitability has also been suggested for integration into REDD?+?(reducing emissions from deforestation, forest degradation and enhancement of forest C stocks) currently being negotiated under the United Nations FCCC. We assess the aboveground C sequestration potential of four major plantation crops – cocoa (Theobroma cacao), oil palm (Elaeis guineensis), rubber (Hevea brasiliensis), and orange (Citrus sinesis) – cultivated in the tropics. Measurements were conducted in Ghana and allometric equations were applied to estimate biomass. The largest C potential was found in the rubber plantations (214 tC/ha). Cocoa (65 tC/ha) and orange (76 tC/ha) plantations have a much lower C content, and oil palm (45 tC/ha) has the lowest C potential, assuming that the yield is not used as biofuel. There is considerable C sequestration potential in plantations if they are established on land with modest C content such as degraded forest or agricultural land, and not on land with old-growth forest. We also show that simple C assessment methods can give reliable results, which makes it easier for developing countries to partake in REDD?+ or other payment schemes.     

长期施肥对棕壤有机碳储量及固碳速率的影响

利用棕壤肥料长期定位试验,研究了不同施肥条件下棕壤有机碳在0~60 cm土层的含量和储量特征以及土壤固碳速率.试验共设6个处理,即氮磷肥有机肥配施(M_2NP)、氮肥有机肥配施(M_2N)、单施有机肥(M_2)、单施氮肥(N)、氮磷肥配施(NP)和不施肥处理(CK).结果表明:经过31年长期不同施肥,各处理土壤有机碳(SOC)含量和储量的剖面分布均呈现随土层深度增加而显著降低的规律.本试验条件下M_2NP、M_2N、M_2、NP、N、CK处理的耕层有机碳富集系数分别为0.465、0.455、0.407、0.48_2、0.393、0.471,表明耕层土壤对有机碳的保持强度最强.在0~60 cm土层土壤有机碳储量表现为M_2NP、M_2NM_2、NPNCK,有机肥和化肥配施能够显著提高土壤有机碳含量和储量.与试验前相比,CK处理各土层土壤有机碳含量和储量均显著降低.各处理碳库管理指数(CPMI)表现为M_2NPM_2NM_2NNPCK.分析不同施肥处理土壤固碳速率可知,与试验前相比,CK处理表现为碳的净释放,固碳速率达-401.4 kg·hm~(-_2)·a~(-1);固碳速率最高的为M_2NP,M_2N,分别达到489kg·hm~(-_2)·a~(-1)、440._2 kg·hm~(-_2)·a~(-1).综合结果表明,化肥、有机肥配施所产生交互效应更有利于棕壤有机碳储量的增加及固碳速率的提高.     

Long-term impact of a gliricidia-maize intercropping system on carbon sequestration in southern Malawi

Tree/crop systems under agroforestry practice are capable of sequestering carbon (C) in the standing biomass and soil. Although studies have been conducted to understand soil organic C increases in some agroforestry technologies, little is known about C sequestered in simultaneous tree/crop intercropping systems. The main objective of this study was to determine the effect of agroforestry practice on C sequestration and CO₂-C efflux in a gliricidia-maize intercropping system. The experiment was conducted at an experimental site located at the Makoka Agricultural Research Station, in Malawi. The studies involved two field plots, 7-year (MZ21) and 10-year (MZ12), two production systems (sole-maize and gliricidia-maize simultaneous intercropping systems). A 7-year-old grass fallow (Grass-F) was also included. Gliricidia prunings were incorporated at each time of tree pruning in the gliricidia-maize. The amount of organic C recycled varied from 0.8 to 4.8 Mg C ha⁻¹ in gliricidia-maize and from 0.4 to 1.0 Mg C ha⁻¹ in sole-maize. In sole-maize, net decreases of soil carbon of 6 Mg C ha⁻¹ at MZ12 and 7 Mg C ha⁻¹ at MZ21 in the topsoil (0–20 cm) relative to the initial soil C were observed. After 10 years of continuous application of tree prunings C was sequestered in the topsoil (0–20 cm) in gliricidia-maize was 1.6 times more than in sole-maize. A total of 123–149 Mg C ha⁻¹ were sequestered in the soil (0–200 cm depth), through root turnover and pruning application in the gliricidia-maize system. Carbon dioxide evolution varied from 10 to 28 kg ha⁻¹ day⁻¹ in sole-maize and 23 to 83 kg ha⁻¹ day⁻¹ in gliricidia-maize. We concluded that gliricidia-maize intercropping system could sequester more C in the soil than sole-maize.     

Dynamics and the economics of carbon sequestration: common oversights and their implications

Accurate assessment of the cost of carbon sequestration is important for the development of mitigation policies globally. Given that sequestration in soils or vegetation is a lengthy process, such assessment requires financial discounting and making realistic assumptions about changes over time in the rate of sequestration, the price of carbon, and the opportunity cost incurred by adopting sequestration practices. Our objective is to demonstrate how these assumptions affect estimates of the cost of sequestration-based mitigation strategies. Using an Australian case study of soil carbon sequestration, our estimates of the carbon price required for financial viability are highly sensitive to dynamic assumptions, varying by a factor of four with different assumptions. Yet the influence of these time-related assumptions is poorly acknowledged in the literature, with many studies either failing to disclose their assumptions, or employing questionable assumptions and methods. Recommended global strategies are for researchers to report their assumptions related to dynamics much more transparently and to improve their research methods and the realism of their assumptions when analysing the economics of carbon sequestration. We recommend that policymakers become better aware of the issues created by dynamics, so that they are able to validly interpret assessments of the cost of sequestration and to ensure that they design policies in a way that facilitates fair comparison of the costs of mitigation strategies that operate over different timescales.     

Soil carbon sequestration and associated economic costs for farming systems of the Indo-Gangetic Plain: A meta-analysis

Soil organic carbon sequestration rates over 20 years based on the Intergovernmental Panel for Climate Change (IPCC) methodology were combined with local economic data to determine the potential for soil C sequestration in wheat-based production systems on the Indo-Gangetic Plain (IGP). The C sequestration potential of rice-wheat systems of India on conversion to no-tillage is estimated to be 44.1 Mt C over 20 years. Implementing no-tillage practices in maize-wheat and cotton-wheat production systems would yield an additional 6.6 Mt C. This offset is equivalent to 9.6% of India's annual greenhouse gas emissions (519 Mt C) from all sectors (excluding land use change and forestry), or less than one percent per annum. The economic analysis was summarized as carbon supply curves expressing the total additional C accumulated over 20 year for a price per tonne of carbon sequestered ranging from zero to USD 200. At a carbon price of USD 25 Mg C⁻¹, 3 Mt C (7% of the soil C sequestration potential) could be sequestered over 20 years through the implementation of no-till cropping practices in rice-wheat systems of the Indian States of the IGP, increasing to 7.3 Mt C (17% of the soil C sequestration potential) at USD 50 Mg C⁻¹. Maximum levels of sequestration could be attained with carbon prices approaching USD 200 Mg C⁻¹ for the States of Bihar and Punjab. At this carbon price, a total of 34.7 Mt C (79% of the estimated C sequestration potential) could be sequestered over 20 years across the rice-wheat region of India, with Uttar Pradesh contributing 13.9 Mt C.     

Monitoring and economic factors affecting the economic viability of afforestation for carbon sequestration projects

The Kyoto Protocol is the first step towards achieving the objectives of the United Nations Framework Convention on Climate Change and aims among others to promote ‘the protection and enhancement of carbon sinks and reservoirs’. To encourage afforestation for carbon sequestration a project must be economically viable. This study uses a model to analyse the impact on project viability of a range of carbon monitoring options, international carbon credit value and discount rate, applied to a Pinus radiata afforestation project in New Zealand. Monitoring carbon in conjunction with conventional forest inventory shows the highest return. Long-term average carbon accounting has lower accounting costs, compared to annual and 5 yearly accounting, as monitoring is only required every 5–10 years until the long-term average is attained. In this study we conclude that monitoring soil carbon stocks is not economically feasible using any of the accounting methods, when carbon is valued at US$ 10/t. This conclusion may be relevant to forest carbon sequestration projects elsewhere in the world and suggests care is needed in selecting the appropriate carbon monitoring options to avoid the risk that costs could be higher than any monetary benefits from terrestrial carbon sequestration. This would remove any commercial incentive to afforest for carbon sequestration reasons and severely limit the use of forest sinks as part of any package of measures addressing the ultimate objective of the UNFCCC.     

Analysis of leakage in carbon sequestration projects in forestry: a case study of upper magat watershed,Philippines

The role of forestry projects in carbon conservation and sequestration is receiving much attention because of their role in the mitigation of climate change. The main objective of the study is to analyze the potential of the Upper Magat Watershed for a carbon sequestration project. The three main development components of the project are forest conservation: tree plantations, and agroforestry farm development. At Year 30, the watershed can attain a net carbon benefit of 19.5 M tC at a cost of US$ 34.5 M. The potential leakage of the project is estimated using historical experience in technology adoption in watershed areas in the Philippines and a high adoption rate. Two leakage scenarios were used: baseline and project leakage scenarios. Most of the leakage occurs in the first 10 years of the project as displacement of livelihood occurs during this time. The carbon lost via leakage is estimated to be 3.7 M tC in the historical adoption scenario, and 8.1 M tC under the enhanced adoption scenario.     

Optimizing carbon sequestration in commercial forests by integrating carbon management objectives in wood supply modeling

This paper provides a methodology for generating forest management plans, which explicitly maximize carbon (C) sequestration at the forest-landscape level. This paper takes advantage of concepts first presented in a paper by Meng et al. (2003; Mitigation Adaptation Strategies Global Change 8:371–403) by integrating C-sequestration objective functions in existing wood supply models. Carbon-stock calculations performed in Woodstock^TM (RemSoft Inc.) are based on C yields generated from volume table data obtained from local Forest Development Survey plots and a series of wood volume-to-C content conversion factors specified in von Mirbach (2000). The approach is used to investigate the impact of three demonstration forest-management scenarios on the C budget in a 110,000 ha forest in south-central New Brunswick, Canada. Explicit demonstration scenarios addressed include (1) maximizing timber extraction either by clearcut or selection harvesting for greatest revenue generation, (2) maximizing total C storage in the forest landscape and in wood products generated from harvesting, and (3) maximizing C storage together with revenue generation. The level of clearcut harvesting was greatest for scenario 1 (≥15 × 10⁴ m³ of wood and ≥943 ha of land per harvesting period), and least for scenario 2 (=0 m³ per harvesting period) where selection harvesting dominated. Because softwood saw logs were worth more than pulpwood ($60 m⁻³ vs. $40 m⁻³) and were strategic to the long-term storage of C, the production of softwood saw logs exceeded the production of pulpwood in all scenarios. Selection harvesting was generally the preferred harvesting method across scenarios. Only in scenario 1 did levels of clearcut harvesting occasionally exceed those of selection harvesting, mainly in the removal of old, dilapidated stands early in the simulation (i.e., during periods 1 through 3). Scenario 2 provided the greatest total C-storage increase over 80 years (i.e., 14 × 10⁶ Mg C, or roughly 264 Mg ha⁻¹) at a cost of $111 per Mg C due to lost revenues. Scenarios 3 and 1 produced reduced storage rates of roughly 9 × 10⁶ Mg C and 3 × 10⁶ Mg C, respectively; about 64% and 22% of the total, 80-year C storage calculated in scenario 2. The bulk of the C in scenario 2 was stored in the forest, amounting to about 76% of the total C sequestered.     

Potential and sustainability for carbon sequestration with improved soil management in agricultural soils of China

Arable land soils generally have lower organic carbon (C) levels than soils under native vegetation; increasing the C stocks through improved management is suggested as an effective means to sequester CO₂ from the atmosphere. China's arable lands, accounting for 13% of the world's total, play an important role in soil C sequestration, but their potential to enhance C sequestration has not yet been quantitatively assessed. The C sequestration by agricultural soils is affected by many environmental factors (such as climate and soil conditions), biological processes (crop C fixation, decomposition and transformation), and crop and soil management (e.g. tillage and manure application). Estimation of the C sequestration potential requires the quantification of the combined effects of these factors and processes. In this study, we used a coupled remote sensing- and process-based ecosystem model to estimate the potential for C sequestration in agricultural soils of China and evaluated the sustainability of soil C uptake under different soil management options. The results show that practicing no-tillage on 50% of the arable lands and returning 50% of the crop residue to soils would lead to an annual soil C sequestration of 32.5 Tg C, which accounts for about 4% of China's current annual C emission. Soil C sequestration with improved soil management is highly time-dependent; the effect lasted for only 20–80 years. Generally, practicing no-tillage causes higher rate and longer sustainability of soil C sequestration than only increasing crop residue into soils. The potential for soil C sequestration varied greatly among different regions due to the differences in climate, soil conditions and crop productivity.     

基于城市污水资源化的微藻筛选与污水预处理

利用城市污水培养微藻,可在实现污水无害化处理的同时,培养微藻回收生物质能源.污水为微藻的培养提供氮、磷等营养组分和所需水源.由于城市污水含有大量的微生物,成分复杂,且不同藻种对污水的适应性与耐受性不同,因此,需要筛选出适宜于城市污水培养和高效产脂的藻种,并研究城市污水预处理方式,以使预处理后的城市污水更适于微藻的生长与产脂.本文根据课题组前期获得的藻种在城市污水中的生长与产脂情况以及对污水的净化能力筛选出适宜于城市污水培养的藻种.其中斜生栅藻(Scenedesmus obliquus)原始株与蛋白核小球藻(Chlorella pyrenoidosa)离子诱变藻株生物质与油脂产量较高,经污水培养后油脂产量分别可达0.43 g·L~(-1)、0.33 g·L~(-1),且含有较多的C16~C18脂肪酸,适宜于生物柴油的制备,同时可使培养后污水中COD、NH_4~+-N、TN、TP的去除率分别达到86.4%、100%、94.3%、93.4%和81.8%、100%、94.9%、94.2%.对可规模化扩大的污水预处理方式进行研究,发现不同藻种所最适的污水预处理方式不同.对于耐污性能较强的斜生栅藻原始株,除去粗大悬浮物后的城市污水即可用于其培养.对于蛋白核小球藻诱变株,城市污水经沉淀、过滤联合预处理后适宜于其培养.