• Authors:
    • Tran,T.
    • Da,G.
    • Moreno-Santander,M. A.
    • Velez-Hernandez,G. A.
    • Giraldo-Toro,A.
    • Piyachomkwan,K.
    • Sriroth,K.
    • Dufour,D.
  • Source: Resources, Conservation & Recycling
  • Volume: 100
  • Year: 2015
  • Summary: Energy use, water use and greenhouse gas (GHG) emissions were assessed for the transformation of cassava roots into starch by two small-scale (ST1, ST2: 1-2 t starch per day) and one large-scale (VLT: 100-200 t starch per day) technologies. The goal of the study was to identify hotspots of energy use and GHG emissions, as well as sustainable practices, with a view to uncover opportunities to improve the environmental performance of cassava starch production. VLT required 2527 MJ/t starch, mainly (77%) from biogas used to dry starch, but was the most efficient in terms of water use (10 m 3/t starch) due to the practice of water recycling between unit operations. ST1 and ST2 were similar in terms of electricity use (212 MJ/t starch), and were able to rely on solar energy to dry starch, due to the small volumes of production. In contrast, water use varied from 21 to 62 m 3/t starch due to differences in the design of the rasping and starch recovery (extraction) operations. GHG emissions were 149, 93 and 105 kg CO 2eq/t starch for VLT, ST1 and ST2 respectively. For ST1 and ST2, methane emissions from untreated wastewater were the main contribution to GHG emissions. For VLT, methane was captured to produce biogas and to dry starch, and the main contribution to GHG emissions was the use of non-renewable grid electricity. Biogas technology was adopted in the past 12 years in the case of VLT. Previously fuel oil was used instead of biogas, which resulted in GHG emissions of 539 kg CO 2eq/t starch. VLT used markedly more electricity than ST1 and ST2, which was necessary to ensure the high output and consistent starch quality. Strategies to reduce the impacts of cassava starch production could focus on (1) increasing the energy efficiency of the drying operation, in order to make more biogas available for other uses such as production of renewable electricity; (2) improving the design of some unit operations with regards to water and energy efficiency; and (3) promoting the transfer and adoption of water recycling practices.
  • Authors:
    • Nhung, N.
  • Source: Journal
  • Volume: 20
  • Issue: 6
  • Year: 2015
  • Summary: Enhancing carbon sequestration is crucial to mitigate rising global levels of greenhouse gases, and for developing countries, carbon sequestration may also provide economic benefits via international carbon trading schemes. This study aimed to determine the optimal management strategy for tropical planted forests when timber and carbon sequestration are valued. The survey data were collected from 291 household foresters, who were growing Eucalyptus urophylla and Acacia mangium in Yen Bai Province, Vietnam. The regression exercise suggests that financial status was negatively correlated with forest management practices, and ethnicity and financial status were correlated with carbon sequestration management. The survey results suggest that the mean rotation age employed by household foresters is five years. However, the optimization modelling suggests that the optimal rotation age for maximizing net present value is greater than nine years. The differences between current practices and optimal practices therefore favour a role for government policy interventions.
  • Authors:
    • Managanvi, K.
    • Erayya
    • Makanur, B
    • Jagdish, J.
  • Source: Environment and Ecology
  • Volume: 31
  • Issue: 2
  • Year: 2013
  • Summary: The evidence for climate change is now considered to be unequivocal, and trends in atmospheric carbon dioxide (CO 2), temperature and sealevel rise are tracking the upper limit of model scenarios elaborated in the Fourth Assessment (AR4) undertaken by the International Panel on Climate Change (IPCC). Agriculture directly contributes almost 14% of total Green House Gas (GHG) emissions and indirectly accounts for a further 7% incurred by the conversion of forests to agriculture (mostly conversion to rangeland in the Amazon), currently at the rate of 7.3 million ha/year. It focuses on specific aspects of agriculture and agricultural water management that contribute to greenhouse gas emissions and offer prospects for mitigation. In addition to the impacts of cycles of wetting and drying, the concentration of inorganic and organic fertilizer on land with some form of water management means that the practice of irrigation has scope to mitigate GHG emissions. Global atmospheric temperature is predicted to rise by approximately 4°C by 2080, consistent with a doubling of atmospheric CO 2 concentration. Increased atmospheric concentrations of CO 2 enhance photosynthetic efficiency and reduce rates of respiration, offsetting the loss of production potential due to temperature rise. Early hopes for substantial CO 2 mitigation of production losses due to global warming have been restrained. A second line of reasoning is that by the time CO 2 levels have doubled, temperatures will also have risen by 4°C, negating any benefit.
  • Authors:
    • Luo, J. F.
    • Ding, W. X.
    • Cai, Y. J.
  • Source: GEODERMA
  • Volume: 181
  • Year: 2012
  • Summary: There is a high spatial variation in N2O emission from agricultural fields and N2O emissions from fields cultivated with stalk-crops was generally measured in the interrow area. The aim of this study was to evaluate the difference in seasonal N2O emissions between interrow soil and interrow + row soil, and to understand the effect of different fertilizers on N2O emissions in a maize-cultivated sandy loam soil in the North China Plain. The experiment included five treatments: organic manure (OM), half-organic manure N plus half fertilizer N (HOM), fertilizer NPK (NPK), fertilizer NK (NK) and control (CK). Cumulative N2O emission from interrow + row soil during the maize growth season was 0.84-122 kg N ha(-1) with an average of 0.98 kg N ha(-1) in the N-fertilized treatments, significantly higher than the 0.30-0.49 kg N ha(-1) from interrow soil. However, no significant difference was observed in the CK treatment. The measurement in interrow soil underestimated N2O emissions by 44-67%. This difference mainly occurred at the two peak emission periods following fertilizer application probably due to discrepancy in soil denitrification potential. Manure application more efficiently increased difference in N2O emission between interrow soil and interrow + row soil than inorganic N fertilizer application. The higher NO concentration did not induce larger N2O emission from interrow soil in the NK treatment than in the NPK treatment, but did from interrow + row soil, resulting in greater difference in N2O emission between interrow soil and interrow + row soil. It is suggested that measuring N2O emission solely from interrow soil could underestimate seasonal N2O emissions, and partly mask the effect of N fertilizer application rates on N2O emission in a maize-cultivated soil in the North China Plain.
  • Authors:
    • Jouquet, P.
    • Doan, T.
    • Rumpel, C.
    • Ngo, P.
  • Source: Soil Biology and Biochemistry
  • Volume: 50
  • Year: 2012
  • Summary: The use of organic matter (OM) amendments is widespread in tropical countries and may be beneficial for soil carbon storage. Interactions between earthworms and OM amendments in tropical soils are largely unknown. The aim of this study was to investigate the effect of bioturbation on the quantity and chemical composition of OM in soil amended with compost and vermicompost. Our approach included comparison of soil samples amended with compost, vermicompost or chemical fertilizers in the presence or absence of earthworms during a one-year greenhouse experiment. The soils were submitted to a regular cultivation cycle. After one year, we analysed bulk samples for soil OM elemental composition and characterised its lignin and non-cellulosic carbohydrate components. Our results showed a decrease of the carbon and nitrogen content in soil amended with chemical fertilizers. Vermicompost amendment led to unchanged OC content, whereas the compost amendment increased the soils OC content compared to initial soil. The addition of earthworms reduced OC and N content in soils with organic amendments. This is in contrast to soil amended with mineral fertilizer only, where the presence of earthworms did not have any effect. Bioturbation influenced the lignin signature of the soils, and to a lesser extent the non-cellulosic carbohydrate signature. In conclusion, compost amendment combined with bioturbation influenced the quality and quantity of SOM and as result carbon storage and its biogeochemical cycling in tropical soils. Implications for soil fertility remain to be elucidated.
  • Authors:
    • Duc, T. T.
    • De Rouw, A.
    • Valentin, C.
    • Jouquet, P.
    • Orange, D.
    • Tureaux, T. H. des
    • Huon, S.
    • Hai, A. P. H.
  • Source: Geoderma
  • Volume: 177
  • Year: 2012
  • Summary: In Vietnam soil erosion is a major environmental problem with respect to soil fertility, water quality and downstream property damages and involves 40% of total land surface. Due to a continuous and persistent decrease of soil quality under annual crops, farmers gradually convert their fields to grazing lands and their crops to fodder cultures or tree plantations. Experimental 1-m(2) field plots with three replicates each were monitored for two years (2006-2007) to evaluate the impact of three different fodder treatments (Paspalum atratum, Panicum maximum and Stylosanthes guianensis) on runoff and soil detachment in a cultivated catchment of North Vietnam. These experiments were designed to monitor at local scale the protective effect of vegetation cover against splash and rain-impacted erosion. The lowest runoffs (ca. 3.0-4.4%), sediment yields (ca. 14-19 g m(-2) yr(-1)) and soil organic carbon losses (ca. 0.7 g C m(-2) a(-1)) were obtained for P. maximum that provided the best soil protection with respect to the two other treatments. These values were low as compared to cultivated crops (cassava and rainfed rice). Soil surface characteristics (mainly biological activity and crusting) did apparently not play a key role, most likely because each plant cover provided, with its own efficiency, protection against rainfall erosivity and rapid plant regrowth wiped out traces of flow detachment. The extent of soil detachment and sediment export, mainly controlled by cut and carry operations of fodder management, was reduced by increasing slope length from 1 to 5 m. The choice of dense fodders such as P. maximum appears to be, in terms of improved livelihood and environment sustainability, an interesting issue for uplands farmers. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Andrasko, K.
    • Bosquet, B.
  • Year: 2010
  • Authors:
    • Nguyen, V. T.
    • Valentin, C.
    • Jouquet, P.
    • Orange, D.
    • Podwojewski, P.
    • Janeau, J. L.
    • Tran, D. T.
  • Source: CATENA
  • Volume: 74
  • Issue: 2
  • Year: 2008
  • Summary: Two consecutive years of investigation on soil surface features, surface runoff and soil detachment within 1-m(2) microplots on 40% slope highlighted the effects of land-use change, vegetation cover and biological activity on the water pathways in Northern Vietnam. Three replicate plots were setup on each of five land-uses: cassava (CAS), grass fodder of Bracharia ruziziensis (BRA), a 3-year old fallow (FAL), tree stands of Acacia mangium and Venicia montana (FOR), and a fallow with regrowth of Eucalyptus regularly cut (EUC). The second year, two of the microplots under FAL and EUC were treated with herbicide (FALh, EUCh), one of them was burnt (FALh+b, EUCh+b). The highest yearly surface runoff coefficient of 16%, and soil detachment rate of 700 g m(-2) yr(-1) in average with a maximum of 1305 g m(-2) yr(-1) have been recorded under CAS. On FALh and FALh+b, runoff ratios were 8.7 and 13.5%, respectively and detachment rates were 86 and 389 g m(-2). On FAL and BRA the yearly runoff ratio varied from 5.9 to 9.8% but the detachment rate was limited at 24 to 35 g m(-2). FOR and EUC annual runoff was