Assessment of the influence of energy density and feedstock transport distance on the environmental performance of methane from maize silages

Environmental and socio-economic performance of intensive farming systems with varying agricultural resource for maize production

The challenge of meeting the rising food demand and the need for achieving this through environment friendly and socio-economically acceptable strategies has posed an unprecedented pressure on the current intensive farming systems. Evidence for integrating the environmental burden and socio-economic profit is lacking. This study quantifies the yield performance, environmental burden (in terms of seven mid-point environmental impact categories, especially for the global warming potential (GWP) in terms of greenhouse gas emissions), and economic benefits among different intensive farming systems with varying agricultural resource input in maize (Zea mays) production. The results showed that seed yields increased with increasing resource inputs under intensive farming systems. Meanwhile, environmental burden in terms of GWP and integrated environmental impacts (IEI) based on per unit grain yield produced increased substantially with increasing resource inputs. The conventional planting accomplished the worst environmental performance (represented by the highest IEI), which was mainly attributed to higher agricultural resource input (such as fertilizer and diesel fuel consumption) per unit of grain yield produced, and thereby increased GWP, abiotic depletion-elements (Ade), ozone layer depletion (ODP), photochemical oxidation (PO), acidification potential (AP), and eutrophication potential (EP) by 22 %, 30 %, 36 %, 25 %, 32 % and 35 %, respectively. The relatively lower resource input under intensive farming coupled with water-saving technology could be highly recommended to local farmers; while extreme resource input planting patterns were not endorsed because of the yield penalty, low net revenue and high environmental burden. This study highlights the importance of an appropriate use of agricultural resources and innovative water-saving technology for mitigating environmental perils and ensuring global food supplies under intensive farming systems.

Bioenergy from anaerobic digestion plants: Energy and environmental assessment of a wide sample of Italian plants

This study assesses the energy and environmental performances of electricity produced from Italian anaerobic digestion coupled with combined heat and power plants. The Life Cycle Assessment methodology is applied to a set of plants characterised by different power sizes (from 100 to 999 kW) and feedstock compositions (variable rates of agricultural products and by-products). Then, the average eco-profile of the produced electricity is compared with electricity produced by the national grid and photovoltaic panels. The analysis allows detection of the combinations of size and feedstock with the lowest impacts. They correspond to small and medium plants mainly fed by organic by-products. In addition, compared to electricity from the grid, the average biogas electricity is characterised by the lowest contribution in impacts categories, such as abiotic depletion potential and ozone layer depletion potential, while largest in acidification and eutrophication. Focusing on global warming potential and cumulative energy demand fossil, the impacts of average biogas electricity (155 kgCO_2eq/MWh and 172 MJ/MWh) are about 35 % and 38 % of that generated by the grid. Furthermore, it could generate 47 % less of the impact in the abiotic depletion elements category of the solar system. To enhance the farms' environmental and economic sustainability and balance the electric grid, these outcomes point out that biogas electricity produced from the agriculture and livestock sector can contribute to the decarbonisation and self-sufficiency of European countries. The results strictly depend on the operative conditions and can aid policymakers at the global level in improving the energy supply security and sustainability. Further, they provide reliable information to stakeholders to select the most sustainable solution, according to the feedstock type, power supply, and management.

The Identification of Hotspots in the Bioenergy Production Chain

Increasing interest in bioenergy production in the context of the transition towards a circular economy and the promotion of renewable energy has produced demands for optimization of the value chain of energy production to improve the environmental viability of the system. Hotspot analysis based on life cycle assessment (LCA) contributes to the mitigation of environmental burdens and is a very important step towards the implementation of a bioeconomy strategy. In this study, hotspots identified using two parallel pathways: a literature review and empirical research on four different biogas plants located in Poland. LCA and energy return on investment (EROI) analysis of the whole bioenergy production chain were considered to identify unit processes or activities that are highly damaging to the environment. The biogas plants differ mainly in the type of raw materials used as an input and in the method of delivery. The results show that the most impactful processes are those in the delivery of biomass, especially road transport by tractor. The second contributor was crop cultivation, where fossil fuels are also used. Although the EROI analysis indicates a negligible impact of transport on the energy efficiency of bioenergy plants, the environmental burden of biomass transportation should be taken into consideration when planning further measures to support the development of the bioeconomy.

Evaluation of Eco-Efficiency of Two Alternative Agricultural Biogas Plants

Implementation of the circular economy is one of the priorities of the European Union, and energy efficiency is one of its pillars. This article discusses an effective use of agri-food industry waste for the purposes of waste-to-energy in biogas plants. Its basic objective is the comparative assessment of the eco-efficiency of biogas production depending on the type of feedstock used, its transport and possibility to use generated heat. The environmental impact of the analysed installations was assessed with the application of the Life Cycle Assessment (LCA) methodology. Cost calculation was performed using the Levelized Cost of Electricity (LCOE) method. The LCA analysis indicated that a biogas plant with a lower level of waste heat use where substrates were delivered by wheeled transport has a negative impact on the environment. The structure of distributed energy production cost indicates a substantial share of feedstock supply costs in the total value of the LCOE ratio. Thus, the factor affecting the achievement of high eco-efficiency is the location of a biogas plant in the vicinity of an agri-food processing plant, from which the basic feedstock for biogas production is supplied with the transmission pipeline, whereas heat is transferred for the needs of production processes in a processing plant or farm.

Evaluation of anaerobic degradation, biogas and digestate production of cereal silages using nylon-bags

In this study, the degradation efficiency and the biogas and digestate production during anaerobic digestion were evaluated for the cereal silages most used to feed biogas plants. To this purpose, silages of: maize from the whole plant, maize from the ear, triticale and wheat were digested, inside of nylon bags, in laboratory scale digesters, for 75days. Overall, the test involved 288 nylon bags. After 75days of digestion, the maize ear silage shows the highest degradation efficiency (about 98%) while wheat silage the lowest (about 83%). The biogas production ranges from 438 to 852Nm(3)/t of dry matter for wheat and ear maize silage, respectively. For all the cereal silages, the degradation as well as the biogas production are faster at the beginning of the digestion time. Digestate mass, expressed as percentage of the fresh matter, ranges from 38% to 84% for wheat and maize ear silage, respectively.

Life cycle assessment on biogas production from straw and its sensitivity analysis

This study aims to investigate the synthetically environmental impacts and Global Warming Potentials (GWPs) of straw-based biogas production process via cradle-to-gate life cycle assessment (LCA) technique. Eco-indicator 99 (H) and IPCC 2007 GWP with three time horizons are utilized. The results indicate that the biogas production process shows beneficial effect on synthetic environment and is harmful to GWPs. Its harmful effects on GWPs are strengthened with time. Usage of gas-fired power which burns the self-produced natural gas (NG) can create a more sustainable process. Moreover, sensitivity analysis indicated that total electricity consumption and CO2 absorbents in purification unit have the largest sensitivity to the environment. Hence, more efforts should be made on more efficient use of electricity and wiser selection of CO2 absorbent.

Anaerobic digestion and milking frequency as mitigation strategies of the environmental burden in the milk production system

The aim of the study was to assess, through a cradle to farm gate Life Cycle Assessment, different mitigation strategies of the potential environmental impacts of milk production at farm level. The environmental performances of a conventional intensive dairy farm in Northern Italy (baseline scenario) were compared with the results obtained: from the introduction of the third daily milking and from the adoption of anaerobic digestion (AD) of animal slurry in a consortium AD plant. The AD plant, fed only with animal slurries coming also from nearby farms. Key parameters concerning on-farm activities (forage production, energy consumptions, agricultural machines maintenance, manure and livestock management), off-farm activities (production of fertilizers, pesticides, bedding materials, purchased forages, purchased concentrate feed, replacement animals, agricultural machines manufacturing, electricity, fuel) and transportation were considered. The functional unit was 1kg fat and protein corrected milk (FPCM) leaving the farm gate. The selected environmental impact categories were: global warming potential, acidification, eutrophication, photochemical oxidation and non-renewable energy use. The production of 1kg of FPCM caused, in the baseline scenario, the following environmental impact potentials: global warming potential 1.12kg CO2 eq; acidification 15.5g SO2 eq; eutrophication 5.62g PO4(3-) eq; photochemical oxidation 0.87g C2H4 eq/kg FPCM; energy use 4.66MJeq. The increase of milking frequency improved environmental performances for all impact categories in comparison with the baseline scenario; in particular acidification and eutrophication potentials showed the largest reductions (-11 and -12%, respectively). In anaerobic digestion scenario, compared to the baseline one, most of the impact potentials were strongly reduced. In particular the most important advantages were in terms of acidification (-29%), global warming (-22%) and eutrophication potential (-18%). The AD of cow slurry is confirmed as an effective strategy to mitigate the environmental impact of milk production at farm level.