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As a solution to mitigate the effects of climate change, scientists have been looking for more environmentally friendly energy production alternatives, so, since the 2000s, renewable energy production has increased across Europe. Climate change has a negative impact on our planet, with increased emissions of greenhouse gases contributing to global warming. In this context, biogas has become a promising solution for reducing greenhouse gas emissions and improving environmental quality. The purpose of the study is to review the evolution of research and development in this field, identify trends and gaps in existing knowledge, and assess the impact and significance of published research. In this sense, a bibliometric analysis was carried out, based on the topics "renewable energy" and "biogas", in which VosViewer software was used to create maps. The research results show that existing policies worldwide encourage transfer and synergy between researchers from different countries, achieving important results. Practically, researches and examples of good practise show that biogas can be a viable solution to mitigate the effects of climate change, and in the coming decades, under the conditions of the population growth estimates materialization, we will most likely witness an intensification of agriculture to ensure the population's food needs. [ABSTRACT FROM AUTHOR]

There are many options for the utilization of biogas in different energy sectors (power, heat, mobility). The technical possibilities of using biogas are more diverse than the actual business models applied in the biogas industry. This paper shows the possible utilization pathways of biogas, divided into coupled power and heat generation, direct utilization and upgrading to a gas of a higher value. Subsequently, an overview of the business models discussed is given by a systematic literature review. The latter shows that the investigation of biogas business models is focused mainly on the last decade and has increased slightly over time. The regions of investigation can be found worldwide, with a clear focus on Europe. Direct use is studied mainly in the Asian and African regions. In the European context, a shift from investigating combined heat and power use to upgrading the biogas produced is evident. [ABSTRACT FROM AUTHOR]

The European Commission has been currently working towards a form of mobility that is sustainable, energyefficient and respectful of the environment. The scope is to reduce the adverse effects connected to mobility. A special attention must be payed to implementing more sustainable modes of transport, which must become more efficient and attractive. Simultaneously, innovative methods and technologies for energy saving and for the environment protection must be introduced. This paper makes an analysis of the best practices and measures proposed at European level to promote sustainable transport in urban centres, recommendations addressed to citizens and local authorities based on the best practices and successful projects implemented in some European cities. There are emphasized some organizing and planning measures for developing urban transport by adopting green solutions and mobility initiatives, aimed to reduce the air pollution, to use the urban area and the energy resources more efficiently. The paper also presents several case studies of European cities where policies of sustainable transport were implemented successfully. They may be regarded as successful examples for adopting green mobility practices in Romania. [ABSTRACT FROM AUTHOR]

Silphium perfoliatum is a perennial crop native to North America that has been the subject of increased scientific interest in recent years, especially in Europe. It is drought- and frost-resistant, which makes it suitable for cultivation in Europe on marginal lands that are not used for growing other crops. This review analyzed the distribution and purposes of the cultivation of Silphium perfoliatum worldwide, as well as its biomass yields and characteristics as a feedstock for biogas production and other purposes. A total of 121 scientific publications on Silphium perfoliatum were identified, with the highest number (20 papers) published in 2019. It was found that higher biomass yields can be obtained at higher precipitation levels, with the use of fertilizers and an adequate type of plantation. The mean dry matter yield of Silphium perfoliatum was 13.3 Mg ha−1 DM (dry matter), and it ranged from 2 to over 32 Mg ha−1 DM. In some countries, Silphium is used as a forage crop mainly due to its high crude protein content (from 4.9% to 15% DM), depending on the vegetation phase. Silphium perfoliatum is a promising perennial crop in terms of energy and other benefits for biodiversity, soil quality and applications in medicine and pharmacology. [ABSTRACT FROM AUTHOR]

Currently an increasing demand for renewable energy can be observed. A part of this demand could be covered by the production of energy from agrarian biomass. Due to the limited availability of arable land, food and feed production are starting to compete for agrarian resources. A way out of this dilemma is to develop concepts that are based on otherwise unused agrarian biomass like straw and include new technologies for the fermentation of lignocellulosic biomass. In this paper, the energy potentials of two different cropping systems are compared. In the energy-based crop rotation system all crops were used either for biogas or ethanol production. In the biorefinery-based approach, the various crops were used in cascades for the production of food as well as feed. Experimental laboratory work and field trials were combined to calculate energy and biomass yields of the crops under investigation. The results demonstrate that steam explosion pretreatment of wheat straw led to a 30% increase in the specific methane yield. The calculated energy output of the biorefinery-based crop rotation system amounted to a total of 126 GJ ha−1 year−1. Extrapolating this energy output to the total arable land of the EU-27 member states, 13,608 PJ of energy could be produced. Therefore, biorefinery-based crop rotation systems could provide approximately three times more energy to the European population than energy-based crop rotation systems. [ABSTRACT FROM AUTHOR]

Biogas is expected to contribute 10% of the total renewable energy use in Europe in 2030. This expectation largely depends on the use of several biomass byproducts and wastes as feedstocks. However, the current development of a biobased economy requires biomass sources for multiple purposes. If alternative applications also use biogas feedstocks, it becomes doubtful whether they will be available for biogas production. To explore this issue, this paper aims to provide an overview of potential alternative uses of different biogas feedstocks being researched in literature. We conducted a literature review using the machine learning technique "co-occurrence analysis of terms". This technique reads thousands of abstracts from literature and records when pairs of biogas feedstock-application are co-mentioned. These pairs are assumed to represent the use of a feedstock for an application. We reviewed 109 biogas feedstocks and 217 biomass applications, revealing 1053 connections between them in nearly 55,000 scientific articles. Our results provide two insights. First, a large share of the biomass streams presently considered in the biogas estimates have many alternative uses, which likely limit their contribution to future biogas production. Second, there are streams not being considered in present estimates for biogas production although they have the proper characteristics. [ABSTRACT FROM AUTHOR]

Abstract: Energy production from anaerobic digestion of organic waste and dedicated digestable biomass is a promising climate change mitigation option. Over the last ten years anaerobic digestion has become established in many European countries. The plants have been developed for renewable energy generation, but also to control the emission of odors from zootechnical farms and to stabilize biomass before its agronomic use. In Italy the subsidies available for power generation from biomass have given rise to renewed interest in biogas, creating new opportunities for the agricultural and livestock sectors. Despite of this, in Southern Italy the manure is highly dispersed over a large number of small-size cattle farms, while power generation facilities are affected by scale economies and the aggregation of input biomass is a major logistic, managing, economic and environmental drawback towards the diffusion of such technologies. In this paper, an investment decision methodology for the assessment of optimal size and feedstock mix of biogas power plants fed by cattle manure and energy crops is presented. The methodology is applied to one of the most promising basins of Puglia region, in Southern Italy, represented by the Municipalities of the Local Action Group “Terra dei Trulli e del Barsento”, Province of Bari. The main factors influencing the profitability of these investments are assessed, with biogas power plant size ranging between 50kW and 1MW, and on the basis of the recently introduced feed-in tariff scheme for such plants (D.M. 6 July 2012). The results show that a high manure recovery rate, the reuse of biogas slurry and the cogeneration options are major key factor for the profitability of the investments. [Copyright &y& Elsevier]

Anaerobic digestion is a well known process that (while still capable of showing new features) has experienced several waves of technological development. It was "born" as a wastewater treatment system, in the 1970s showed promise as an alternative energy source (in particular from animal waste), in the 1980s and later it became a standard for treating organic-matter-rich industrial wastewater, and more recently returned to the market for its energy recovery potential, making use of different biomasses, including energy crops. With the growing concern around global warming, this paper looks at the potential of anaerobic digestion in terms of reduction of greenhouse gas (GHG) emissions. The potential contribution of anaerobic digestion to GHG reduction has been computed for the 27 EU countries on the basis of their 2005 Kyoto declarations and using life cycle data. The theoretical potential contribution of anaerobic digestion to Kyoto and EU post-Kyoto targets has been calculated. Two different possible biogas applications have been considered: electricity production from manure waste, and upgraded methane production for light goods vehicles (from landfill biogas and municipal and industrial wastewater treatment sludges). The useful heat that can be produced as by-product from biogas conversion into electricity has not been taken into consideration, as its real exploitation depends on local conditions. Moreover the amount of biogas already produced via dedicated anaerobic digestion processes has also not been included in the calculations. Therefore the overall gains achievable would be even higher than those reported here. This exercise shows that biogas may considerably contribute to GHG emission reductions in particular if used as a biofuel. Results also show that its use as a biofuel may allow for true negative GHG emissions, showing a net advantage with respect to other biofuels. Considering also energy crops that will become available in the next few years as a result of Common Agricultural Policy (CAP) reform, this study shows that biogas has the potential of covering almost 50% of the 2020 biofuel target of 10% of all automotive transport fuels, without implying a change in land use. Moreover, considering the achievable GHG reductions, a very large carbon emission trading "value" could support the investment needs. However, those results were obtained through a "qualitative" assessment. In order to produce robust data for decision makers, a quantitative sustainability assessment should be carried out, integrating different methodologies within a life cycle framework. The identification of the most appropriate policy for promoting the best set of options is then discussed. [ABSTRACT FROM AUTHOR]

Focuses on the biogenic gas production in tidal European estuaries. Distribution of major biogases liable to have environment consequences; Use of equilibrator technique.

This paper proposes a bottom-up method to estimate the technical capacity of solid oxide fuel cells to be installed in wastewater treatment plants and valorise the biogas obtained from the sludge through an efficient conversion into electricity and heat. The methodology uses stochastic optimisation on 200 biogas profile scenarios generated from industrial data and envisages a Pareto approach for an a posteriori assessment of the optimal number of generation unit for the most representative plant configuration sizes. The method ensures that the dominant role of biogas fluctuation is included in the market potential and guarantees that the utilization factor of the modules remains higher than 70% to justify the investment costs. Results show that the market potential for solid oxide fuel cells across Europe would lead up to 1,300 MW of installed electric capacity in the niche market of wastewater treatment and could initiate a capital and fixed costs reduction which could make the technology comparable with alternative combined heat and power solutions. • We integrate solid-oxide fuel cells (SOFCs) in wastewater treatment (WWT). • SOFCs are efficient co-generation devices but hindered by high capital costs. • Technical SOFC potential in Europe WWT, up to 1370 MW, may promote cost reduction. [ABSTRACT FROM AUTHOR]

• Green CO 2 potential in Europe for bio−CCU applications evaluated. • Evaluation of fossil CO 2 sources in Europe available for CCU. • 69.7 Mt/a CO 2 estimated for upgraded biogas and combustion and fermentation processes. • 506.7 Mt/a green CO 2 available - seven times the current CO 2 demand. • Discussion of limitations such as gas purity, capture cost and competitive use. This study investigates the theoretical potential and limitations of carbon dioxide sources for technical valorisation approaches. On the one hand the emission of greenhouse gases, especially CO 2 , must be rigorously reduced in order to achieve the European and global climate objectives. On the other hand, CO 2 is becoming increasingly valuable as a resource for industries and new disrupting technologies on CO 2 utilization. Therefore, the potential of CO 2 obtained from different biogenic and fossil sources in Europe is discussed for a comparative evaluation. These sources are classified according to their emitting processes and industry sectors, respectively. The resulting valorisation potentials are then calculated from statistical data for CO 2 generating processes in Europe, complemented and verified by relevant papers and reports. This study demonstrates the European potential of capturing and utilizing biogenic and fossil CO 2. In Europe, 69.7 Mt/a CO 2 are estimated to be produced by biogas upgrading, biogas combustion, as well as bioethanol and other fermentation processes. Additionally, 437 Mt/a CO 2 are produced by solid biomass combustion. This accounts for a theoretical potential of up to 506.7 Mt/a biogenic CO 2 currently available, which is nearly seven times the amount of the current European industrial CO 2 demand. The utilization potentials from these theoretical amounts are limited by attainable capture rates, reaching from 10 % to 90 % primarily depending on the dilution of the emitting source. [ABSTRACT FROM AUTHOR]

In order to promote China's biogas industry development, this paper comprehensively compared the biogas status and related policies between China and Europe and tried to find the shortage and potential implications. China has access to abundant biomass resources, with considerable biogas potential and an annual theoretical output of 73.6 billion m3. Household-based biogas digesters coexist with medium and large-scale biogas plants (MLBPs) in China. Although the number of MLBPs in China was almost two times higher than Europe, the annul biogas production yield was only half of those in Europe. In China, biogas is mainly used for heating and cooking, and its power generation capacity is far lower than that in Europe. Overall, biogas industry is more commercialized in Europe than China. In terms of biogas related policies, China has an advantage in quantity, but is weak in their implementation. Biogas related policies in China mainly focus on agricultural and rural development, while in Europe, they are aimed at increasing the utilization of renewable energy and reducing greenhouse gas emissions. In addition, policies in China are mostly filled with encouragement, lacking detailed subsidy schemes and modes, whereas in European countries are more targeted and scientific. Based on the dissimilarity of current status and the disparity in policies, a series of countermeasures and suggestions for the development of the Chinese biogas industry are presented. • China's biomass sources have lower utilization rate compared to Europe. • Biogas industry in Europe is more industrialized and commercialized than in China. • The related-biogas policy framework of Europe is more mature and perfect. • European biogas policy provide valuable reference for China's biogas development. • China's biogas industry has great potential for development. [ABSTRACT FROM AUTHOR]

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This article examines how local experiments and negotiation processes contribute to social and field-level learning. The analysis is framed within the niche development literature, which offers a framework for analyzing the relation between projects in local contexts and the transfer of local experiences into generally applicable rules. The authors examine 2 case studies drawn from a meta-analysis of 27 new energy projects. The case studies, both pertaining to biogas projects for local municipalities, illustrate the diversity of applications for a technology through processes of local variation and selection. The authors examine the diversity of expectations and the negotiation and alignment of these expectations underlying the diversity of local solutions. Moreover, the authors address how the transfer of lessons from individual local experiments can follow different pathways and yet always require due attention to the social and cultural limits to the transferability of solutions. [ABSTRACT FROM AUTHOR]

Combining organic farming and biogas production from agricultural feedstocks has been suggested as a way of achieving carbon (C) neutrality in Europe. However, as the long-term effects of C removal for methane production on soil organic carbon (SOC) are unclear, organic farmers in particular have questioned whether farm biogas production will have a positive effect on soil fertility. Eight years of data from an organic long-term field trial involving digestate fertilisation and various crop rotations (CRs) with differing proportions of clover-grass leys were used to calculate C inputs based on the CANDY model, and these modelled changes compared with measured changes in SOC content (SOCc) over the same period. Measured SOCc increased by nearly 20% over the eight years. Digestate fertilisation significantly increased SOCc. Fertilised plots with the highest proportion of clover-grass in the CR had the highest SOCc. The C inputs from clover-grass leys, even if they only made up 25% of the CR, were high enough to increase SOCc, even with the removal of all aboveground biomass and without fertilisation. Our results show that biogas production based on clover-grass leys could be an important part of sustainable farming, improving or maintaining SOCc and improving nutrient flows, particularly in organic farming, while simultaneously providing renewable energy. [ABSTRACT FROM AUTHOR]