Exploring the production of bio-energy from wood biomass. Italian case study.

Sara González-García, Jacopo Bacenetti

The concerns related to the environmental impact related to energy production from fossil fuel are increasing. In this context, the substitution of fossil fuel based energy by bio-energy can be an effective solution. In this study, the production of electricity and heat in Italy in a combined heat and power plant (CHP) based on an Organic Rankine Cycle (ORC) turbine from wood based biomass both from forest and agricultural activities has been analysed considering four potential alternative scenarios to the current energy status: biomass from very short rotation forestry (VSRF) poplar and willow stands as well as residues from natural forests and from traditional poplar plantations. The evaluation has been performed by applying Life Cycle Assessment (LCA) method and an attributional cradle-to-gate approach has been followed. The expected savings of greenhouse gases emission and fossil fuels demand have been quantified, as well as derived emissions of toxic pollutants and substances responsible for acidification, eutrophication and photochemical oxidant formation. The results have been also compared with the conventional Italian scenario considering the current Italian electricity profile and heat production from natural gas. Among the different scenarios, due to the lower transport distance, the use of biomass from traditional poplar plantation residues shows the lowest impact. The biomass combustion emissions are the main hotspot for several evaluated impact categories (e.g., particulate matter formation, human toxicity). In fact, when the produced bio-energy is compared to the reference system (i.e., electricity produced under the Italian electric profile) the results do not favor bio-energy systems. The results reported in this study support the idea that forest residues would be an interesting and potential feedstock for bio-energy purposes although further research is required specifically with the aim of optimizing biomass supply distances.

Click here to read the article.

Estimating the environmental impacts of a brewery waste–based biorefinery: Bio-ethanol and xylooligosaccharides joint production case study

Sara González-García, Pablo Comendador Morales, Beatriz Gullón

In the food industry, the brewing sector holds a strategic economic position since beer is the most consumed alcoholic beverage in the world. Brewing process involves the production of a large amount of lignocellulosic residues such as barley straw from cereal cultivation and brewer’s spent grains. This study was aimed at developing a full-scale biorefinery system for generating bio-ethanol and xylooligosaccharides (XOS) considering the mentioned residues as feedstock. Life Cycle Assessment (LCA) methodology was used to investigate the environmental consequences of the biorefinery system paying special attention into mass and energy balances in each production section to gather representative inventory data. Biorefinery system was divided in five areas: i) reconditioning and storage, ii) autohydrolysis pretreatment, iii) XOS purification, iv) fermentation and v) bioethanol purification. LCA results identified two environmental hotspots all over the whole biorefinery chain: the production of steam required to achieve the large autohydrolysis temperature (responsible for contributions higher than 50% in categories such as acidification and global warming potential) and the production of enzymes required in the simultaneous saccharification and fermentation (> 95% of contributions to terrestrial and marine aquatic ecotoxicity potentials). Since enzymes production involves high energy intensive background processes, the most straightforward improvement challenge should be focused on the production of steam. An alternative biorefinery scenario using wood chips as fuel source to produce heating requirements instead of the conventional natural gas was environmentally evaluated reporting improvements ranging from 44% to 72% in the categories directly affected by this hotspot.

Click here to read the article.

BioSA: Production of Bio-Succinic Acid from Apple Pomace Using an Environmental Approach

Sara González-García, Lucía Argiz, Patricia Míguez, Beatriz Gullón

Fermentation-derived bio-succinic acid (BioSA) is a valuable intermediate; it is used as a chemical building block, and has multiple industrial applications as an alternative to petroleum counterparts.

The aim of this study was to develop a full-scale plant to produce BioSA from apple pomace, a low-cost solid waste from the cider- and juice-making industry, based on a biorefinery concept, and to determine its environmental profile using a cradle- to-factory-gate, scaled-up LCA approach.

Foreground data used in this LCA were based on mass and energy flows, modelled in detail.

The production process was divided into three stages:

  1. reconditioning and storage;
  2. fermentation with Actinobacillus succinogenes;
  3. purification.

The results indicate that the use of enzymes is responsible for the highest environmental burdens, due to their highly energy-intensive background production processes. When these were excluded from the analysis (following other studies available in the literature), the purification stage played an environmentally significant role, due to the extraction and distillation units involved. The electricity use and the requirements for organic solvents in these operations make up the largest environmental burdens. Thus, approaches with the highest potential for improvement must involve both operations.

Alternatives for improvement are proposed that offer interesting potential reductions in the environmental profile, especially at the purification stage.

Click here to read the article.