Environmental performances of giant reed (Arundo donax L.) cultivated in fertile and marginal lands: A case study in the Mediterranean

Perennial rhizomatous grasses (PRGs) tend to have a high yield combined with a low environmental impact. Cultivation in marginal or poorly cultivated land is recommended in order not to compromise food security and to overcome land use controversies. However, the environmental impacts of using different types of soil are still unclear. We thus assessed the environmental impact of two giant reed (GR) systems cultivated in a fertile soil (FS) and in a marginal soil (MS) through a cradle-to-plant gate LCA. We analyzed energy balance, GHG emissions (including LUC, not including iLUC), and the main impacts on air, water and soil quality. In both systems the annualized soil carbon sequestration was more than twofold the total GHG emitted, equal to −6464 kg CO₂eq ha⁻¹ in FS and −5757 kg CO₂eq ha⁻¹ in MS. Overall, soil characteristics affected not only GR yield level, but also its environmental impact, which seems to be higher in the MS system both on a hectare and tonne basis. The production of GR biomass in marginal soil could thus lead to higher environmental impacts and a more extensive land requirement.     

Influence of Aguamiel (Agave atrovirens) as a Natural Feed Additive on Cecal Fermentation Kinetics of Some Forage Species in Horse Feeding

This study aimed to evaluate the effect of different dose levels of aguamiel (Agave atrovirens) on in vitro cecal gas, methane (CH₄), and carbon dioxide (CO₂) productions of five forage species (Avena sativa [hay]), Moringa oleifera, Caesalpinia coriacea, Salix babylonica, and Eichhornia crassipes using inocula from the horse. The forage samples were incubated with three doses of aguamiel: 0, 34, and 68 μg of aguamiel/g dry matter (DM) of substrate. Cecal inocula were collected from four adult female Criolla horses (3–4 years of age and weighing 300 ± 15.0 kg) grazed on native grasses for about 8 hours without supplementation. Forage type affected (P < .001) cecal asymptotic, rate and lag time of gas, CH₄ and CO₂ productions (mL/g DM), pH and DM degradability. Aguamiel dose had linear and quadratic effects (P < .05) on the asymptotic and rate of CH₄ productions and rate and lag time of CO₂ productions (mL/g DM). Forage type × aguamiel dose interactions were significant (P < .05) for asymptotic, rate and lag time of gas, and CH₄ and CO₂ productions (mL/g DM). Forage species effects were pronounced (P < .05) on CH₄ and CO₂ productions (mL/g incubated and degraded DM) and proportional CH₄ production at all hours of incubation, except for CO₂ production (mL/g incubated DM). Aguamiel dose affected (P < .05) CO₂ production (mL/g incubated DM) and proportional CO₂ production at the incubated hours. Forage type × aguamiel dose interactions were observed (P < .05) for CO₂ production (mL/g incubated DM) and proportional CO₂ production at the incubated hours but had no impact on CH₄ production. It is concluded that addition of aguamiel to five forage species affected fermentation kinetics of gas production resulting in different in vitro cecal gas, CH₄ and CO₂ productions from these substrates.     

区域工业发展与碳排放的脱钩关系分析——基于2006~2013年湖南的实际情况

根据湖南省“十一五”以来（2006~2013年）的工业发展和碳排放情况，分析湖南工业发展与碳排放之间的脱钩弹性、节能弹性、减排弹性，结果表明：湖南工业行业发展的过程中，较好地控制了碳排放量，但节能减排任务依然较大。因此，新常态下应以“节能、减排”为主线，深入优化产业结构，调整能源消费结构，从而确保工业可持续发展的同时，实现碳排放的合理控制。     

Carbon stocks and carbon fluxes from a 10‐year prescribed burning chronosequence on a UK blanket peat

Prescribed burning is a common land management technique in many areas of the UK uplands. However, concern has been expressed at the impact of this management practice on carbon stocks and fluxes found in the carbon‐rich peat soils that underlie many of these areas. This study measured both carbon stocks and carbon fluxes from a chronosequence of prescribed burn sites in northern England. A range of carbon parameters were measured including above ground biomass and carbon stocks; net ecosystem exchange (NEE), net ecosystem respiration (R_eco) and photosynthesis (P_g) from closed chamber methods; and particulate organic carbon (POC). Analysis of the CO₂ data showed that burning was a significant factor in measured CO₂ readings but that other factors such as month of sampling explained a greater proportion of the variation in the data. Carbon budget results showed that whereas all the plots were net sources of carbon, the most recent burn scars were smaller sources of carbon compared with the older burn scars, suggesting that burning of Calluna‐dominated landscapes leads to an ‘avoided loss’ of carbon. However, this management intervention did not lead to a transition to a carbon sink and that for carbon purposes, active peat‐forming conditions are desirable.     

Greater humification of belowground than aboveground biomass carbon into particulate soil organic matter in no-till corn and soybean crops

Quantifying the amount of carbon (C) incorporated from decomposing residues into soil organic carbon (C_S) requires knowing the rate of C stabilization (humification rate) into different soil organic matter pools. However, the differential humification rates of C derived from belowground and aboveground biomass into C_S pools has been poorly quantified. We estimated the contribution of aboveground and belowground biomass to the formation of C_S in four agricultural treatments by measuring changes in δ¹³C natural abundance in particulate organic matter (C_POM) associated with manipulations of C₃ and C₄ biomass. The treatments were (1) continuous corn cropping (C₄ plant), (2) continuous soybean cropping (C₃), and two stubble exchange treatments (3 and 4) where the aboveground biomass left after the grain harvest was exchanged between corn and soybean plots, allowing the separation of aboveground and belowground C inputs to C_S based on the different δ¹³C signatures. After two growing seasons, C_POM was primarily derived from belowground C inputs, even though they represented only ∼10% of the total plant C inputs as residues. Belowground biomass contributed from 60% to almost 80% of the total new C present in the C_POM in the top 10 cm of soil. The humification rate of belowground C inputs into C_POM was 24% and 10%, while that of aboveground C inputs was only 0.5% and 1.0% for soybean and corn, respectively. Our results indicate that roots can play a disproportionately important role in the C_POM budget in soils. Keywords Particulate organic matter; root carbon inputs; carbon isotopes; humification rate; corn; soybean.     

Energy use and greenhouse gas emissions from turf management of two Swedish golf courses

Turf management on golf courses entails frequent maintenance activities, such as mowing, irrigation and fertilisation, and relies on purchased inputs for optimal performance and aesthetic quality. Using life cycle assessment (LCA) methodology, this study evaluated energy use and greenhouse gas (GHG) emissions from management of two Swedish golf courses, divided into green, tee, fairway and rough, and identified options for improved management. Energy use and GHG emissions per unit area were highest for greens, followed by tees, fairways and roughs. However, when considering the entire golf course, both energy use and GHG emissions were mainly related to fairway and rough maintenance due to their larger area. Emissions of GHG for the two golf courses were 1.0 and 1.6 Mg CO₂e ha⁻¹ year⁻¹ as an area-weighted average, while the energy use was 14 and 19 GJ ha⁻¹ year⁻¹. Mowing was the most energy-consuming activity, contributing 21 and 27% of the primary energy use for the two golf courses. In addition, irrigation and manufacturing of mineral fertiliser and machinery resulted in considerable energy use. Mowing and emissions associated with fertilisation (manufacturing of N fertiliser and soil emissions of N₂O occurring after application) contributed most to GHG emissions. Including the estimated mean annual soil C sequestration rate for fairway and rough in the assessment considerably reduced the carbon footprint for fairway and turned the rough into a sink for GHG. Emissions of N₂O from decomposition of grass clippings may be a potential hotspot for GHG emissions, but the high spatial and temporal variability of values reported in the literature makes it difficult to estimate these emissions for specific management regimes. Lowering the application rate of N mineral fertiliser, particularly on fairways, should be a high priority for golf courses trying to reduce their carbon footprint. However, measures must be adapted to the prevailing conditions at the specific golf course and the requirements set by golfers.     

Evaluation of direct and indirect phosphorus limitation of methanogenic pathways in a calcareous subtropical wetland soil

The effect of phosphorus (P) and carbon (C) on methanogenesis was investigated in a low-P (130 mg P kg⁻¹ soil) wetland within Everglades National Park. Soil was amended with C substrates (acetate, formate, butyrate, and glucose) with or without P, and CO₂ and CH₄ production was monitored. Production of CH₄ increased with P addition although no effect on CO₂ was observed. Methane production was stimulated by all C substrates except for butyrate. No effect of C on CO₂ production was observed except for stimulation following glucose addition. Production of CH₄ following formate addition was not affected by P, suggesting hydrogenotrophic methanogens may be substrate, not P, limited. Addition of P to all other C substrates heightened CH₄ production and lowered the CO₂–C:CH₄–C ratio relative to the corresponding C only treatment, suggesting that P may have limited acetoclastic methanogens and fermentation.     

Can carbon sequestration markets benefit low-income producers in semi-arid Africa? Potentials and challenges

The Clean Development Mechanism (CDM) of the Kyoto Protocol of the United Nations Framework Convention on Climate Change allows a country that emits C above agreed-upon limits to purchase C offsets from an entity that uses biological means to absorb or reduce greenhouse emissions. The CDM is currently offered for afforestation and reforestation projects, but may apply subsequently to sequestration in agricultural soils. Additionally, markets outside of the Protocol are developing for soil C sequestration.     

岩溶地区生态环境可持续发展的生态足迹分析

本文以西南岩溶地区清镇市为例,采用生态足迹的理论和模型对2005年清镇市区域生态足迹状况进行了测算和分析,并与不同区域进行比较。结果表明:①清镇市2005年的人均生态足迹为2.5440hm2,超过了它的人均生态承载力;②清镇市2005年人均生态赤字为2.1240hm2,表明清镇市处于一种不可持续的发展状态;③清镇市2005年万元GDP生态足迹为2.8139hm2,高于中国西部的平均水平,资源利用为粗放消耗型。针对清镇市生态赤字的状况,提出了缓解该市生态压力、提高生态承载力的建议。     

Comparative economic performance and carbon footprint of two farming models for producing Atlantic salmon (Salmo salar): Land-based closed containment system in freshwater and open net pen in seawater

Ocean net pen production of Atlantic salmon is approaching 2 million metric tons (MT) annually and has proven to be cost- and energy-efficient. Recently, with technology improvements, freshwater aquaculture of Atlantic salmon from eggs to harvestable size of 4–5 kg in land-based closed containment (LBCC) water recirculating aquaculture systems (RAS) has been demonstrated as a viable production technology. Land-based, closed containment water recirculating aquaculture systems technology offers the ability to fully control the rearing environment and provides flexibility in locating a production facility close to the market and on sites where cost of land and power are competitive. This flexibility offers distinct advantages over Atlantic salmon produced in open net pen systems, which is dependent on access to suitable coastal waters and a relatively long transport distance to supply the US market. Consequently, in this paper we present an analysis of the investment needed, the production cost, the profitability and the carbon footprint of producing 3300 MT of head-on gutted (HOG) Atlantic salmon from eggs to US market (wholesale) using two different production systems—LBCC-RAS technology and open net pen (ONP) technology using enterprise budget analysis and carbon footprint with the LCA method. In our analysis we compare the traditional open net pen production system in Norway and a model freshwater LBCC-RAS facility in the US. The model ONP is small compared to the most ONP systems in Norway, but the LBCC-RAS is large compared to any existing LBCC-RAS for Atlantic salmon. The results need to be interpreted with this in mind. Results of the financial analysis indicate that the total production costs for two systems are relatively similar, with LBCC-RAS only 10% higher than the ONP system on a head-on gutted basis (5.60 US$/kg versus 5.08 US$/kg, respectively). Without interest and depreciation, the two production systems have an almost equal operating cost (4.30 US$/kg for ONP versus 4.37 US$/kg for LBCC-RAS). Capital costs of the two systems are not similar for the same 3300 MT of head-on gutted salmon. The capital cost of the LBCC-RAS model system is approximately 54,000,000 US$ and the capital cost of the ONP system is approximately 30,000,000 US$, a difference of 80%. However, the LBCC-RAS model system selling salmon at a 30% price premium is comparatively as profitable as the ONP model system (profit margin of 18% versus 24%, respectively), even though its 15-year net present value is negative and its return on investment is lower than ONP system (9% versus 18%, respectively). The results of the carbon footprint analysis confirmed that production of feed is the dominating climate aspect for both production methods, but also showed that energy source and transport methods are important. It was shown that fresh salmon produced in LBCC-RAS systems close to a US market that use an average US electricity mix have a much lower carbon footprint than fresh salmon produced in Norway in ONP systems shipped to the same market by airfreight, 7.41 versus 15.22 kg CO₂eq/kg salmon HOG, respectively. When comparing the carbon footprint of production-only, the LBCC-RAS-produced salmon has a carbon footprint that is double that of the ONP-produced salmon, 7.01 versus 3.39 kg CO₂eq/kg salmon live-weight, respectively.