Lidija Čuček

Carbon and nitrogen trade-offs in biomass energy production.

This contribution provides an overview of carbon (CFs) and nitrogen footprints (NFs) concerning their measures and impacts on the ecosystem and human health. The adversarial relationship between them is illustrated by the three biomass energy production applications, which substitute fossil energy production applications: (i) domestic wood combustion where different fossil energy sources (natural gas, coal, and fuel oil) are supplemented, (ii) bioethanol production from corn grain via the dry-grind process, where petrol is supplemented, and (iii) rape methyl ester production from rape seed oil via catalytic trans-esterification, where diesel is supplemented. The life cycle assessment is applied to assess the CFs and NFs resulting from different energy production applications from ‘cradle-to-grave’ span. The results highlighted that all biomass-derived energy generations have lower CFs and higher NFs whilst, on the other hand, fossil energies have higher CFs and lower NFs.

Energy, Water and Process Technologies Integration for the Simultaneous Production of Ethanol and Food from the entire Corn Plant

Abstract This contribution presents the simultaneous integration of different technologies for converting different parts of the corn plant, and integration of energy, water and feedstocks. The traditional dry-grind process is used for obtaining ethanol from corn grains, whilst for the conversion of corn stover to ethanol, gasification using two different paths of syngas conversion is taken into account: syngas fermentation (thermo-biochemical path) and catalytic mixed alcohol synthesis (thermo-chemical path). These processes are modelled in the Mixed-Integer Process Synthesizer (MIPSYN) using mass and energy balances and conversion constraints. Short cut models for the more complex process units are obtained from the detailed ones, as developed by Martin and Grossmann (2011) . The results show that the best integrated process when using the entire corn plant is a combination of the dry-grind process and thermo-chemical conversion. For the base case (18 kg/s of grain and 10.8 kg/s of stover), the optimal scheme is comprised of dry-grind and thermo-chemical conversion technologies. The best integrated process requires only 17 MW of energy, 50 MW of cooling and 1.56 L/L of freshwater, with an ethanol production cost of 0.41

Significance of environmental footprints for evaluating sustainability and security of development

/kg. In the thermal conversion, the integration of energy plays the more important role when reducing production costs. Since the thermo-chemical path enables better heat integration, it is preferred over the thermo-biochemical in spite of the higher yield and sharing of equipment, when using the syngas fermentation path.

Syntheses of sustainable supply networks with a new composite criterion – Sustainability profit

This contribution presents the selected categories of environmental footprints related to the planetary boundaries and threats to human security. The analysis covers the footprint family of indicators that usually consists of ecological, carbon or more precisely greenhouse gas and water footprints and also sometimes the energy footprint. The other assessed footprints that are important for ecosystem health in regard to water, health, food, and land and species security are nitrogen, phosphorus, biodiversity and land footprints, which have already transgressed the planetary boundaries and are therefore outside the safe operating space. The importance of the various footprints is discussed and the simultaneous analysis of footprints is emphasised as a major direction of research and practice. The comprehensive set of environmental impacts, e.g. set of presented footprints in this contribution, should be considered and should incorporate the burdening and unburdening concept from the life cycle perspective. Some applications of the presented environmental footprints are offered, and conclusions and remarks provided for future observation.Graphical Abstract

Overview of environmental footprints

Abstract This study proposes a new concept and a new metric for multi-criteria evaluation of sustainable systems. The new metric, termed “sustainability profit”, is composed of economic, environmental and social indicators. Since all of these are expressed by monetary terms, the different criteria are now merged, and a multi-objective optimization problem can be reduced to a single-objective one. The new concept for measuring sustainability is based on micro-economic (company’s viewpoint) and on wider macro-economic perspectives (combined government’s and company’s viewpoint). The concept and metric presented are illustrated by three examples of supply networks including a large-scale biorefinery supply network. The obtained results give the insights into sustainable technologies from the overall sustainability viewpoint, and also evaluate the stimulations from governments in the form of subsidies and taxes for deployment of (un-)sustainable systems. The results also indicate that this metric provides good compromise solutions between economic, environmental and social pillars of sustainability.

Multi-period Synthesis of a Biorefinery's Supply Networks

With climate change and other negative environmental impacts, there is an increased interest in measuring and reducing environmental burdens. However, the question is how to measure and reduce environmental burdens. Recently, the researchers, organizations, policy-makers, and others are putting forth efforts to develop concepts and metrics measuring environmental sustainability. Among those concepts and metrics, environmental footprints are gaining increasing popularity and play an ever-increasing role in sustainability evaluation and research. Footprints have become ubiquitous for researchers, policy-makers, and the general public. Over the past years, carbon footprint has been used as an environmental protection indicator almost exclusively. Evaluations have moved to include a variety of other footprints; however, there is no generally accepted footprint or footprint family that represents the overall impact on the environment. This chapter gives an overview of environmental footprints as indicators defined to date (June 2014) that can be used to measure sustainability for environmental decision-making.

Large-Scale Biorefinery Supply Network – Case Study of the European Union

Abstract This contribution presents a multi-period synthesis of an optimally-integrated regional biorefinerys supply networks, based on a Mixed-Integer Linear Programming (MILP) model. The production processes from different sources of biomass include first, second, and third generations of biofuels such as bioethanol, biodiesel, hydrogen, Fischer-Tropsch (FT)-diesel, and green gasoline. The aim is to maximize the economically optimal utilization of seasonal and year-round continuously harvested raw materials from regionally-located available biomass resources, by considering the competition between fuels and food production. The proposed multi-period MILP model enables efficient bioenergy network synthesis and optimization. Economically optimal solutions are obtained, with optimal selection of technologies, raw materials, intermediate and final products, and the timely-optimal planning of harvesting, biofuels production, storage, and logistics.

Synthesis of Networks for the Production and Supply of Renewable Energy from Biomass

Abstract This contribution focuses on those renewable sources used within the transportation sector. As in the short-term only biofuels from biomass might provide an alternative that can be implemented (Martin and Grossmann, 2013), this contribution deals with biofuels production. A generic multi-period model is applied for the efficient synthesis of large-scale biorefinery supply networks. This model, which was previously developed by the authors (Cucek et al., 2013), is upgraded using different model reduction techniques (Lam et al., 2011) in order to be applied cross-regionally throughout the European Union (EU). Several first, second, and third generations of biofuel production technologies are considered (Cucek et al., 2013), and applied to a case study of the EU. The results show that miscanthus and algae are particularly promising raw materials for producing biofuels capable to economically substitute significantly more than 10 % of fossil fuels for transportation at the EU level.

Utilisation of waste heat from exhaust gases of drying process

This paper presents a step towards an integrated approach when synthesizing self-sufficient food-and-energy regional networks and utilising multi-functional crops, which can then be used for food and energy production, dedicated energy crops and low-value agricultural co-products, and waste. For the purpose of analysis, the given region is divided into several zones, which are smaller administratively/economically/geographically integrated areas within the region (Lam et al., 2010). The synthesis of energy production and consumption networks is performed using the superstructural approach, supported by mathematical programming methods. The synthesized networks are comprised of agricultural, pre-processing, processing, and distribution sectors. Economical and environmental evaluation is performed and discussed from optimisation, by employing a mixed-integer nonlinear programming MINLP process synthesizer MIPSYN (Kravanja, 2010).

Nitrogen- and Climate Impact-based Metrics in Biomass Supply Chains

Nowadays a lot of low-grade heat is wasted from the industry through the off- and flue-gasses with different compositions. These gases provide the sensitive heat with utilisation potential and latent heat with the components for condensation. In this paper, process integration methodology has been applied to the partly condensed streams. A hot composite curve that represents the gas mixture cooling according to equation of state for real gases was drawn to account the gas-liquid equilibrium. According to the pinch analysis methodology, the pinch point was specified and optimal minimal temperature difference was determined. The location of the point where gas and liquid phases can be split for better recuperation of heat energy within heat exchangers is estimated using the developed methodology. The industrial case study of tobacco drying process off-gasses is analysed for heat recovery. The mathematical model was developed by using MathCad software to minimise the total annualised cost using compact plate heat exchangers for waste heat utilisation. The obtained payback period for the required investments is less than six months. The presented method was validated by comparison with industrial test data.