• Energy Research

Abstract Pyrolysis may be a first step in biomass to biofuels conversion processes. The present study investigated the influence of pressure on the thermal effects associated to biomass pyrolysis. Four energy crops were selected for experimental characterization: corn stalks, poplar, switchgrass Alamo and switchgrass Trailblazer. The heat demand of the pyrolysis process was measured by differential scanning calorimetry at pressures ranging from 0.1 to 4 MPa, using a specifically developed experimental configuration. An increase of the operating pressure resulted in a lower heat demand and in an increase in the final char yield. The results obtained suggest the presence of a competitive mechanism between the endothermic reactions of the primary decomposition process, leading to the formation of volatiles, and the exothermic vapor–solid interactions, leading to secondary char formation.

The slow pyrolysis process of poultry litter was investigated using different experimental and analytical techniques. A fixed bed reactor was used for the simulation of the slow pyrolysis process up to a constant temperature (400–800 °C) under nitrogen flow. Yields of the different product fractions were determined. On-line FTIR techniques were used to detect the most significant compounds in the evolved gas (carbon dioxide, carbon monoxide and methane). GC–MS results allowed the identification of the more important categories of compounds in the liquid condensate (phenols, fatty acids, sterols, N-containing compounds). The fate of nitrogen and sulphur, present in relevant amounts in the original substrate, was investigated: sulphur remains mostly in char at any investigated temperature, while nitrogen is split among the different products, slightly increasing its transfer to the gas phase only at higher pyrolysis temperatures. The energy transfer from the original biomass substrate to the different product fractions was also investigated. The fraction of biomass energy transferred to non-condensable gases raises with pyrolysis temperature and was estimated to be able to thermally sustain the process at 550 °C. The results obtained shed some light on the potential use of the slow pyrolysis process for sanitation and waste-to-energy valorization of poultry litter.

It is easy to predict that in the coming years in Europe biodiesel will play an increasingly important role in the transport sector. The European Commission has set at 10% by 2020 the proportion that biofuels should represent in total fuel used in transport and biodiesel is currently the most widely used biofuel in the European Union. The most common way to produce biodiesel is through transesterification of vegetable oils with methanol; glycerol is the main co-product. Although glycerol has many industrial applications, increased production of biodiesel could make complete market placement of this chemical difficult. In this context, increasing interest is paid towards different methods of biodiesel production that provide alternative co-products. This article offers a “cradle to gate” evaluation of potential environmental impacts caused by an innovative process for the production of DMC-BioD, an alternative biofuel to biodiesel which does not involve the production of glycerol. Transesterification of soybean oil with dimethyl carbonate to obtain DMC-BioD has been modelled with the aid of the Chemical Process Simulation software Aspen HYSYS® that produced the material and energy balances and the preliminary sizing of the process units. Results have been also compared with background information from database on the production of conventional biodiesel from soybean oil and of fossil diesel. The study suggests that DMC-BioD can be an interesting route for the production of biofuels from an environmental point of view. Compared to fossil diesel, GHG (Greenhouse gases) emissions can be decreased, although trade-offs are registered in other environmental categories. In any case, future investigation is needed in order to understand and optimize its environmental profile through the entire life cycle and possibly bring its production to a commercial scale. This preliminary analysis of potential environmental impacts provides useful information to continue the testing and scale-up phases and to improve the environmental performances of the process.

Abstract Removal of acid pollutants (HCl and SO2) is an important stage in waste incineration flue gas cleaning. Several technological options for acid gas neutralisation are currently available in order to comply with the increasingly stringent emission limit values and the choice of the best solution for a specific plant should be based on the economic and environmental considerations implied in the concept of Best Available Technique. The present study analyses and compares state-of-the-art dry, semi-dry and wet process configurations for acid gas removal in waste-to-energy plants. The performance of five representative process schemes was analysed: the streams associated with acid gas emission control were quantified via mass and energy balances and a life cycle perspective was applied in order to evaluate the inputs and outputs of the supply and disposal chains. The analysis pinpoints the key issues in terms of environmental and economic performance of the presented alternatives. Benefits and limits of the alternative technologies are discussed in view of different waste composition. The energy penalty associated with flue gas reheat appears to be the main environmental drawback of wet methods, while the main contribution to the environmental footprint of dry methods is given by the production of solid reactants. Multi-stage treatment systems systematically show lower environmental impacts than the single stage counterparts, but their cost-effectiveness is limited by the disposal cost for the generated solid residues. The provided insights can contribute to a more effective implementation of the strategies of circular economy and cleaner production in the operation of a waste-to-energy plant.

Background, Aim and Scope The increasing concern about environment protection and a broader awareness of the sustainable development issues cause more and more attention to be given to the environmental impacts of products through the different phases of their life cycle. Foods are definitely among the products whose overall environmental performance can be effectively investigated resorting to LCA. A LCA case study was performed in order to detect and quantify the environmental impacts deriving from the life cycle of a lager beer produced by an Italian small brewery, investigating and comparing two packaging options: beer in 20 L returnable stainless steel kegs and beer in 33 cL one way glass bottles.

Abstract The optimal supply chain configuration for biomass production on a given territory is identified by a two-tier approach, which considers both the environmental and the economic points of view. The first tier performs a quick evaluation of the supply chain, based on simplified assumptions and on average values of the parameters characterizing the geographical territory. The second tier allows for the inclusion of spatially explicit parameters of the territory and realizes a more detailed optimization of the supply chain using a multi-objective Mixed Integer Linear Programming framework. A demonstrative case study is presented for the bio-fuel supply to a centralized electric power plant. The considered supply chain is based on miscanthus, cultivated in marginal terrains and converted to pyro-oil in a number of delocalized plants for long distance shipment. The results obtained from the two tiers of the model provide quantitative information, to support quick and effective decision making on the optimal configuration of the supply chain in terms of plant size, location, transport logistics and cultivation.

The development and design of innovative biomass waste to energy conversion processes is a key issue to pursue the implementation of circular economy and to endorse a sustainable management of agricultural land. Assessing the environmental and economic sustainability of such processes is of paramount importance to prevent the trade-off of their impacts. The present study focused on a novel biomass waste to energy conversion process based on thermocatalytic reforming (TCR). Two different agricultural waste substrates (olive wood pruning and digestate) were selected as reference cases for conversion to energy and valuable material fractions. Mass and energy balances allowed the calculation of environmental and economic indexes considering alternative scenarios for the final use of the energy and of the products obtained from the TCR conversion (i.e. syngas, bio-oil and bio-char). A sensitivity analysis was carried out to assess the robustness of results. The overall performances of the TCR process resulted strongly related to the characteristics of the biomass waste and to the possible use of the product fractions obtained in the TCR process. The use of bio-char for soil amendment, allowed by the high quality of bio-char obtained from the TCR, was a key point to improve the expected environmental and economic sustainability of the conversion process.

Abstract The influence of process conditions on the overall heat demand during the pyrolysis of biomass was investigated. The results show that increasing the vapour residence time by an increasing initial sample weight or an increasing operating pressure results in an increasing char yield and in a decreasing heat demand. Lumped reaction schemes were used for data interpretation. They suggest that only an exothermic char formation process may justify the experimental results obtained. Influence of pressure, residence time and initial sample mass on biomass heat demand were correlated to the final char yield, confirming that the formation of char during pyrolysis is an exothermic process, independently of operating conditions.

Life cycle assessment (LCA) is a powerful tool to identify direct and indirect environmental burdens associated with products, processes and services. A critical phase of the LCA methodology is the collection of representative inventory data for the energy and material streams related to the production process. In the evaluation of new and emerging chemical processes, measured data are known only at laboratory scale and may have limited connection to the environmental footprint of the same process implemented at industrial scale. On the other hand, in the evaluation of processes already established at commercial scale, the availability of process data might be hampered by industrial confidentiality. In both cases, the integration of simple process design techniques in the LCA can contribute to overcome the lack of primary data, allowing a more correct quantification of the life cycle inventory. The present paper shows, through the review of case study examples, how simplified process design, modeling and simulation can support the LCA framework to provide a preliminary estimate of energy and material consumption data suitable for environmental assessment purposes. The discussed case studies illustrate the implementation of process design considerations to tackle availability issues of inventory data in different contexts. By evidencing the case-specific nature of the problem of preliminary conceptual process design, the study calls for a closer collaboration of process design experts and life cycle analysts in the green development of new products and processes.