• Energy Research

A rapid method is needed to assess biogas and methane yield potential of various kinds of substrate prior to anaerobic digestion. This study reports near infrared reflectance spectroscopy (NIRS) as a rapid alternative method to the conventional batch methods for prediction of specific biogas yield (SBY), specific methane yield (SMY) and kinetics of biogas yield (k-SBY) of reed canary grass (RCG) biomass. Dried and powdered RCG biomass with different level of maturity was used for biochemical composition analysis, batch assays and NIRS analysis. Calibration models were developed using partial least square (PLS) regression from NIRS spectra. The calibration models for SBY (R(2)=0.68, RPD=1.83) and k-SBY (R(2)=0.71, RPD=1.75) were better than the model for SMY (R(2)=0.53, RPD=1.49). Although the PLS model for SMY was less successful, the model performance was better compared to the models based on chemical composition.

Abstract This study evaluates the quality and performance of compost produced from household biowaste (CBIO), aquatic invasive plants (CAIP) and a mixture of the invasive plants and biowaste (CBAIP) in comparison with mineral fertilizer (NPK) application. The composts were produced using Aerobin 400 Composter with aquatic invasive plant collected from the Owabi dam and solid biowaste from households within the Owabi catchment in the Ashanti Region of Ghana as feedstock. A field experiment in a 35 m x 19 m plot of maize was conducted with 9 treatments of the different compost produced and mineral fertilizers in a randomized complete block design (RCBD) with 4 replications. The results show that the compost types produced have acceptable quality with regards to nutrients (NPK), organic matter (OM), organic carbon (OC), bulk density, porosity, and heavy metal contents (Cu, Zn, Cd, Pb, As, Ni) among other properties. Grain yields following treatment with CAIP (2.06 ± 0.692 tons/ha), CBAIP (2.15± 0.668 tons/ha) and CBIO (2.052 ± 0.915 tons/ha) were similar to grain yields from NPK application (2.55 ± 0.611 tons/ha) but significantly higher than the control (1.34 ± 0.500 tons/ha) at 5%. The results show that the different compost types produced have beneficial impacts on grain yields comparable to NPK application. It is, therefore, concluded that aquatic invasive plants and biowaste are suitable feedstock for the production of high-quality compost that significantly improves grain yields.

Abstract Here, we demonstrate the applicability of national strategies towards massive biogas deployment, through a case study Denmark. First, a variety of sustainable agricultural intensification measures to produce additional biomass resources were investigated; as a result, it was found that the biomass currently used in Denmark's biorefineries (including biogas) could be tripled without compromising soil carbon and inducing little to no land use changes. The degree to which these resources could be mobilized for the biogas sector was analysed through examining the extremes, here labelled as LOW and HIGH biomass-to-biogas scenarios. The resulting biomethane production was calculated considering three combinations of biogas production and upgrading technologies: (i) conventional biogas production and upgrading technologies; (ii) plants with prolonged retention time and conventional upgrading technologies and (iii) as in (ii), but upgrading via biological methanation of carbon dioxide in the biogas, using renewable hydrogen. These scenarios revealed a biomethane potential of 24–111 PJ y−1. The key finding of our study is that only the extreme deployment measures, in terms of biomass and technology, allowed to fulfill the emerging gas demands, namely buffering the deficits from fluctuating power and transport (light- and heavy-duty vehicles, urban buses, coaches), quantified at 95 PJ y−1. Yet, just harnessing the full sustainable potential of animal manure, straw and perennial grass allows to supply half of this demand. In the LOW and HIGH biomass scenarios, doubling the retention time brought an increased methane production of 20% (energy-wise), while this increase was 87% when methanation was added.

Il est essentiel de minimiser les pertes d'azote, d'améliorer les pratiques de gestion des engrais et d'adopter des pratiques agricoles durables pour atténuer les impacts climatiques de l'utilisation des engrais et promouvoir la durabilité agricole. Cette étude visait à traiter les émissions de gaz à effet de serre dans les paysages cacaoyers au Ghana en examinant l'impact des systèmes d'ombrage et des amendements du sol sur la libération de dioxyde de carbone (CO2), de méthane (CH4), d'oxyde nitreux (N2O) et le potentiel global de réchauffement de la planète (GWP). L'étude comprenait deux facteurs : les systèmes d'ombre (pas d'ombre et d'ombre moyenne) et l'amendement du sol (pas d'amendement (T1), engrais minéral seul (T2), engrais minéral + biochar (T3), ½ engrais minéral + compost sans phosphate gemme et ½ engrais minéral + compost avec phosphate gemme (T5)). Le système d'abat-jour n'a pas eu d'influence significative sur les émissions de CO2, de CH4 et de N2O. Les émissions de CO2 étaient plus élevées dans les parcelles modifiées par rapport aux parcelles non modifiées dans les deux écozones. Les applications de ½ engrais minéral + compost (T4 et T5) ont augmenté la production de CH4 dans les deux écozones. Cependant, l'application d'engrais minéral seul (T2) et d'engrais minéral + biochar (T3) a eu des effets variables sur les émissions de CH4 du sol. Des émissions de N2O plus importantes ont été enregistrées dans les parcelles modifiées dans les deux écozones par rapport aux parcelles non modifiées (T1). L'eau du sol et le carbone de la biomasse microbienne (CSM) étaient en corrélation positive avec les flux de CO2 et de CH4 dans les deux écozones où l'eau du sol représentait 48 % des émissions de CH4 dans les écozones humides et le CSM était responsable de 54 et 65 % des émissions de CH4 dans les écozones humides et sèches respectivement. L'application unique d'engrais minéraux (T2) avait le PRG le plus élevé,14,70 et 13,56 kg d'équivalent CO2 ha-1 an-1 x 105 dans l'écozone humide et sèche respectivement. Cette étude apporte des informations précieuses sur le potentiel des systèmes d'ombrage et des amendements du sol pour atténuer les émissions de gaz à effet de serre dans les paysages cacaoyers au Ghana, favorisant ainsi la transition vers des systèmes de production de cacao plus durables et résilients au climat. Minimizar las pérdidas de nitrógeno, mejorar las prácticas de gestión de fertilizantes y adoptar prácticas agrícolas sostenibles son esenciales para mitigar los impactos climáticos del uso de fertilizantes y promover la sostenibilidad agrícola. Este estudio tuvo como objetivo abordar las emisiones de gases de efecto invernadero en los paisajes de cacao en Ghana mediante el examen del impacto de los sistemas de sombra y las enmiendas del suelo en la liberación de dióxido de carbono (CO2), metano (CH4), óxido nitroso (N2O) y el potencial general de calentamiento global (GWP). El estudio consistió en dos factores; sistemas de sombra (sin sombra y sombra media) y enmienda del suelo (Sin enmienda (T1), fertilizante mineral solo (T2), fertilizante mineral + biochar (T3), ½ fertilizante mineral + compost sin fosfato de roca y ½ fertilizante mineral + compost con fosfato de roca (T5)). El sistema de sombra no influyó significativamente en las emisiones de CO2, CH4 y N2O. Las emisiones de CO2 fueron mayores en las parcelas modificadas en comparación con las no modificadas en las dos ecozonas. Las aplicaciones de ½ fertilizante mineral + compost (T4 y T5) aumentaron la producción de CH4 en ambas ecozonas. Sin embargo, la aplicación de fertilizante mineral solo (T2) y fertilizante mineral + biochar (T3) tuvo efectos variables en las emisiones de CH4 del suelo. Se registraron mayores emisiones de N2O en las parcelas modificadas dentro de las dos ecozonas en comparación con las parcelas no modificadas (T1). El agua del suelo y el carbono de biomasa microbiana (MBC) se correlacionaron positivamente con los flujos de CO2 y CH4 en las dos ecozonas donde el agua del suelo representó el 48% de las emisiones de CH4 en las ecozonas húmedas, y el MBC fue responsable del 54 y 65% en las ecozonas húmedas y secas respectivamente, de las emisiones de CH4. La aplicación de fertilizante mineral único (T2) tuvo el GWP más alto,14.70 y 13.56 kg de CO2 eq ha-1 año-1 x 105 tanto en la ecozona húmeda como en la seca, respectivamente. Este estudio aporta información valiosa sobre el potencial de los sistemas de sombra y las enmiendas del suelo para mitigar las emisiones de gases de efecto invernadero en los paisajes de cacao en Ghana, fomentando así la transición hacia sistemas de producción de cacao más sostenibles y resistentes al clima. Minimizing nitrogen losses, improving fertilizer management practices, and adopting sustainable agricultural practices are essential for mitigating the climate impacts of fertilizer use and promoting agricultural sustainability. This study aimed to address greenhouse gas emissions in cocoa landscapes in Ghana by examining the impact of shade systems and soil amendments on the release of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and overall global warming potential (GWP). The study consisted of two factors; shade systems (no shade and medium shade) and soil amendment (No amendment (T1), mineral fertilizer alone (T2), mineral fertilizer + biochar (T3), ½ mineral fertilizer + compost without rock phosphate and ½ mineral fertilizer + compost with rock phosphate (T5)). The shade system did not significantly influence CO2, CH4, and N2O emissions. Emissions of CO2 were higher in the amended compared to the non-amended plots in the two eco-zones. Applications of ½ mineral fertilizer + compost (T4 and T5) increased CH4 production in both eco-zones. However, the application of mineral fertilizer alone (T2) and mineral fertilizer + biochar (T3) had varying effects on CH4 emissions from the soil. Greater emissions of N2O were recorded in the amended plots within the two eco-zones compared to the non-amended (T1) plots. Soil water and microbial biomass carbon (MBC) correlated positively with CO2 and CH4 fluxes in the two eco-zones where soil water accounted for 48% of the emissions of CH4 in the moist eco-zones, and MBC was responsible for 54 and 65% in the moist and dry eco-zones respectively, of CH4 emissions. Sole mineral fertilizer application (T2) had the highest GWP,14.70 and 13.56 kg CO2 eq ha-1 yr-1 x 105 in both the moist and dry eco-zone respectively. This study contributes valuable insights into the potential of shade systems and soil amendments to mitigate greenhouse gas emissions in cocoa landscapes in Ghana, thereby fostering the transition towards more sustainable and climate-resilient cocoa production systems. يعد تقليل خسائر النيتروجين وتحسين ممارسات إدارة الأسمدة واعتماد الممارسات الزراعية المستدامة أمرًا ضروريًا للتخفيف من الآثار المناخية لاستخدام الأسمدة وتعزيز الاستدامة الزراعية. تهدف هذه الدراسة إلى معالجة انبعاثات غازات الدفيئة في المناظر الطبيعية للكاكاو في غانا من خلال دراسة تأثير أنظمة الظل وتعديلات التربة على إطلاق ثاني أكسيد الكربون (CO2) والميثان (CH4) وأكسيد النيتروز (N2O) وإمكانات الاحترار العالمي الإجمالية (GWP). تألفت الدراسة من عاملين ؛ أنظمة الظل (بدون ظل وظل متوسط) وتعديل التربة (بدون تعديل (T1)، الأسمدة المعدنية وحدها (T2)، الأسمدة المعدنية + الفحم الحيوي (T3)، ½ الأسمدة المعدنية + السماد بدون فوسفات الصخور و ½ الأسمدة المعدنية + السماد مع فوسفات الصخور (T5)). لم يؤثر نظام الظل بشكل كبير على انبعاثات ثاني أكسيد الكربون والميثان وأكسيد النيتروز. كانت انبعاثات ثاني أكسيد الكربون أعلى في المناطق المعدلة مقارنة بالمناطق غير المعدلة في المنطقتين الإيكولوجيتين. أدت استخدامات ½ سماد معدني + سماد (T4 و T5) إلى زيادة إنتاج الميثان في كل من المناطق البيئية. ومع ذلك، كان لتطبيق الأسمدة المعدنية وحدها (T2) والأسمدة المعدنية + الفحم الحيوي (T3) تأثيرات متفاوتة على انبعاثات الميثان من التربة. تم تسجيل انبعاثات أكبر من أكسيد النيتروز في قطع الأراضي المعدلة داخل المنطقتين الإيكولوجيتين مقارنة بقطع الأراضي غير المعدلة (T1). ترتبط مياه التربة وكربون الكتلة الحيوية الميكروبية (MBC) ارتباطًا إيجابيًا بتدفقات ثاني أكسيد الكربون والميثان في المنطقتين الإيكولوجيتين حيث شكلت مياه التربة 48 ٪ من انبعاثات الميثان في المناطق الإيكولوجية الرطبة، وكانت MBC مسؤولة عن 54 و 65 ٪ في المناطق الإيكولوجية الرطبة والجافة على التوالي من انبعاثات الميثان. كان لاستخدام الأسمدة المعدنية الوحيدة (T2) أعلى قدرة على إحداث الاحترار العالمي،14.70 و 13.56 كجم من مكافئ ثاني أكسيد الكربون هكتار -1 سنة -1 × 105 في كل من المنطقة البيئية الرطبة والجافة على التوالي. تساهم هذه الدراسة برؤى قيمة حول إمكانات أنظمة الظل وتعديلات التربة للتخفيف من انبعاثات غازات الدفيئة في المناظر الطبيعية للكاكاو في غانا، وبالتالي تعزيز الانتقال نحو أنظمة إنتاج كاكاو أكثر استدامة ومرونة للمناخ.

AbstractThis paper addresses the conversion of Danish agricultural land from food/feed crops to energy crops. To this end, a life cycle inventory, which relates the input and output flows from and to the environment of 528 different crop systems, is built and described. This includes seven crops (annuals and perennials), two soil types (sandy loam and sand), two climate types (wet and dry), three initial soil carbon level (high, average, low), two time horizons for soil carbon changes (20 and 100 years), two residues management practices (removal and incorporation into soil) as well as three soil carbon turnover rate reductions in response to the absence of tillage for some perennial crops (0%, 25%, 50%). For all crop systems, nutrient balances, balances between above‐ and below‐ground residues, soil carbon changes, biogenic carbon dioxide flows, emissions of nitrogen compounds and losses of macro‐ and micronutrients are presented. The inventory results highlight Miscanthus as a promising energy crop, indicating it presents the lowest emissions of nitrogen compounds, the highest amount of carbon dioxide sequestrated from the atmosphere, a relatively high carbon turnover efficiency and allows to increase soil organic carbon. Results also show that the magnitude of these benefits depends on the harvest season, soil types and climatic conditions. Inventory results further highlight winter wheat as the only annual crop where straw removal for bioenergy may be sustainable, being the only annual crop not involving losses of soil organic carbon as a result of harvesting the straw. This, however, is conditional to manure application, and is only true on sandy soils.

Abstract To meet the growing challenges for food security, renewable resource production and climate change adaptation, optimized crop rotations (OCRs) should aim to maximize biomass production and export from the field while minimizing carbon (C) and nitrogen (N) footprints. However, the effects of OCRs on aboveground biomass production and soil C and N stock as well as the potential links between them remain poorly understood. In this study in Denmark, we harvested all aboveground biomass and simultaneously investigated soil C and N content and stock in two continuous monocultures (CMs) as well as in four OCRs. Across five-year continuous observations, OCRs significantly increased cumulative aboveground biomass production by 23% compared to CMs. There was no significant difference between OCRs and CMs in soil C and N content in any of the soil layers (0–20, 20–50, and 50–100 cm) after the five years. Moreover, OCRs had no effect on top layer soil C and N stock compared to CMs, even when examined by equivalent soil mass. Slight reductions in soil C and N stock after five years in both OCRs and CMs did not relate to the changes in aboveground biomass production. Our results highlight that it is feasible to produce more biomass for biorefineries in OCRs than in CMs and the reductions in soil C and N stock over time seem similar for the two systems. Longer-term continuous observations are called for to underpin these results.

Abstract The production of willow in short rotation is expected to result in low nitrate leaching losses as is the case with other permanent crops. However, there is a risk of leaching of nitrate during establishment when the plant cover is limited. Nitrate leaching was followed for three years from the establishment in 1993 of willow (Salix viminalis) at two sites, a coarse sand at Jyndevad and a loamy sand at Foulum. Two levels of nitrogen, 0 or 75 kg N/ha in NPK, were applied annually, though only 38 N/ha was applied in the first year. Leaching was calculated from usually weekly measurements of the nitrate concentration in soil solution and relating with the amount of percolation based on measured precipitation and changes in the soil water content over the sampling periods. Mean leaching for the three periods 1993–94, 1994–95 and 1995–96 amounted to respectively 142, 61 and 0 kg N/ha at Foulum and to 130, 9 and 4 kg N/ha at Jyndevad. The high leaching in the first year was caused by an unusually high content of mineral N in the soil at the start of the experiment. The absence of any leaching 1995–96 at Foulum was due to very low precipitation and a consequent lack of percolation. For the first period (1993–94) the fertilized treatment increased leaching by 32 kg N/ha compared to no fertilizer as a mean of the two sites, while the difference for the following two periods was reduced to 1–2 kg N/ha. It is concluded that application of nitrogen should be avoided in the year of planting of willows, while in the following years75 kg N/ha can be given without risk of increased leaching.

Abstract A prerequisite for successful willow production is a reliable and economically competitive establishment of the crop. Here, we compare different establishment methods including long-term yield effects. A field trial with the new-bred variety Bjorn was established in 1996 and included four establishment methods; 1) vertical planting of standard 0.2 m cuttings; 2) horizontal planting of 0.1 m billets; 3) horizontal planting of 0.2 m billets; 4) horizontal planting of 1.8 m rods. All establishment methods were combined with mechanical and chemical weed control during the establishment year. Dry matter (DM) yield was measured over 6 harvest rotations corresponding to 16 years. In 1st rotation, yield differed significantly between establishment methods with highest yield for 1.8 m rods (10.4 Mg ha−1 year−1), intermediate yield for cuttings and 0.2 m billets (8.6 and 8.5 Mg ha−1 year−1, respectively) and lowest for 0.1 m billets (5.6 Mg ha−1 year−1). No differences were found in 2nd rotation. Over 1st and 2nd rotation, mechanical weed control resulted in significantly lower yield than chemical control when combined with 0.1 m billets. Cuttings and 1.8 m rods were compared over 1st, 2nd, 3rd, 5th and 6th rotation. Rods gave higher yield in 1st rotation, lower yield in 3rd rotation but there were no significant yield differences in 2nd, 5th and 6th rotations, resulting in similar mean yields of 12.4 and 11.9 Mg ha−1 year−1 for cuttings and rods over the whole period. The general yield development over time indicates a relatively stable long-term yield level.