Techno-economic analysis of energy efficiency measures in a pulp mill converted to an ethanol production plant

A conceptual ethanol production plant, based on conversion of a kraft pulp mill, has been studied. The process uses softwood as raw material, alkaline pre-treatment combined with delignification, and biochemical conversion of sugars to ethanol (i.e. hydrolysis and fermentation). The plant has been analysed by pinch methods in order to find steam-saving possibilities. It is shown in the study that a large amount of steam surplus can be found if energy efficiency measures are implemented. In order to study the possible effect on the profitability of the plant when introducing steam-saving measures, the process has been analysed from a techno-economic point of view. It is shown that implementing energy efficiency measures could have a substantial effect on profitability if the by-product (in this case lignin biofuel or power) is high-valued. It is also shown that lignin as by-product might be more profitable than power, mainly because the demand for CO2 in lignin extraction might be supplied by CO2 produced in fermentation of sugars to ethanol. If investments are made to convert a pulp mill to ethanol production, energy efficiency measures should be included in the discussion since they might play an important role in minimising ethanol production cost

Energy-Related Cooperation Projects between Chalmers and Process Industries in West Sweden: A Compilation of Ongoing and Recently Finalized Activities

<p> This report provides an overview of R&D cooperation between Chalmers University of Technology and the process industry on the Swedish West Coast, in many cases also in cooperation with research institutes and regional organisations. This extensive cooperation is, at least in some respects, unique in an international perspective. </p> <p> In order to limit the size of the report, only the process industries with significant cooperation with Chalmers have been included. This cooperation has mainly dealt with activities directed towards energy efficiency and conversion as well as CO2 emissions reduction.</p> <p> The main aims of this report are to: </p> <p> • increase awareness among all stakeholders on the Swedish West Coast about the projects, major actors in different projects as well as major findings so far </p> <p> • increase the awareness within Chalmers about magnitude and breadth of activities (e. g. for identifying new opportunities for multi-disciplinary research) </p> <p> • increase the awareness externally, nationally and internationally, in order to promote increased R&D and industrial cooperation as well as national and international (e. g. EU) funding of unique demonstration projects </p> <p> • identify opportunities for synergy effects and common conclusions between the different projects </p> <p> • provide a platform for discussions on further cooperation areas and forms for such cooperation. </p

The value of flexibility for pulp mills investing in energy efficiency and future biorefinery concepts

Changing conditions in biomass and energy markets require the pulp and paper industry to improve energy efficiency and find new opportunities in biorefinery implementation. Considering the expected changes in the pulp mill environment and the variety of potential technology pathways, flexibility should be a strong advantage for pulp mills. In this context, flexibility is defined as the ability of the pulp mill to respond to changing conditions. The aim of this article is to show the potential value of flexibility in the planning of pulp mill energy and biorefinery projects and to demonstrate how this value can be incorporated into models for optimal strategic planning of such investments. The paper discusses the requirements on the optimization models in order to adequately capture the value of flexibility. It is suggested that key elements of the optimization model are multiple points in time where investment decisions can be made as well as multiple scenarios representing possible energy price changes over time. The use of a systematic optimization methodology that incorporates these model features is illustrated by a case study, which includes opportunities for district heating cooperation as well as for lignin extraction and valorization. A quantitative valuation of flexibility is provided for this case study. The study also demonstrates how optimal investment decisions for a pulp mill today are influenced by expected future changes in the markets for energy and bioproducts

Integration of algae-based biofuel production with an oil refinery: Energy and carbon footprint assessment

Biofuel production from algae feedstock has become a topic of interest in the recent decades since algae biomass cultivation is feasible in aquaculture and does therefore not compete with use of arable land. In the present work, hydrothermal liquefaction of both microalgae and macroalgae is evaluated for biofuel production and compared with transesterifying lipids extracted from microalgae as a benchmark process. The focus of the evaluation is on both the energy and carbon footprint performance of the processes. In addition, integration of the processes with an oil refinery has been assessed with regard to heat and material integration. It is shown that there are several potential benefits of co-locating an algae-based biorefinery at an oil refinery site and that the use of macroalgae as feedstock is more beneficial than the use of microalgae from a system energy performance perspective. Macroalgae-based hydrothermal liquefaction achieves the highest system energy efficiency of 38.6%, but has the lowest yield of liquid fuel (22.5 MJ per 100 MJalgae) with a substantial amount of solid biochar produced (28.0 MJ per 100 MJalgae). Microalgae-based hydrothermal liquefaction achieves the highest liquid biofuel yield (54.1 MJ per 100 MJalgae), achieving a system efficiency of 30.6%. Macro-algae-based hydrothermal liquefaction achieves the highest CO2 reduction potential, leading to savings of 24.5 resp 92 kt CO2eq/year for the two future energy market scenarios considered, assuming a constant feedstock supply rate of 100 MW algae, generating 184.5, 177.1 and 229.6 GWhbiochar/year, respectively. Heat integration with the oil refinery is only possible to a limited extent for the hydrothermal liquefaction process routes, whereas the lipid extraction process can benefit to a larger extent from heat integration due to the lower temperature level of the process heat demand

Evaluating the greenhouse gas impact from biomass gasification systems in industrial clusters – methodology and examples

Biomass gasification is identified as one of the key technologies for producing biofuels for the transport sector and can also produce many other types of products. Biomass gasification systems are large-scale industrial systems and it is important to evaluate such systems from economic, environmental and synergetic perspectives before implementation. The objective of this study is to define a methodology for evaluating the greenhouse gas (GHG) impact of different biomass gasification systems and to exemplify the methodology. The ultimate purpose of the methodology is to evaluate the GHG performance of different biomass gasification systems integrated in industrial clusters. A life cycle perspective is applied. Most biomass gasification systems are multiproduct systems, simultaneously producing biofuels, heat at different temperatures and pressures and electricity. The value, in economic terms and in terms of GHG emissions, is well defined for some products (e.g. biofuels), whereas for other products (such as heat and electricity) it is more uncertain and in some cases dependent on time and location

Economic and greenhouse gas emissions assessment of excess biomass extracted from future kraft pulp mills

Different studies have shown that the process heat requirements of future pulp mills can be satisfied usingavailable internal biomass (bark and lignin), which are process by-products. Assuming that biomass is CO2 neutral, further reducing the process heat demand will not therefore lead to further reduction of Greenhouse Gas (GHG) emissions - unless the excess biomass is extracted and used elsewhere to substitute fossil fuels. Previous work has demonstrated the potential to extract and export significant amounts of biofuel from future pulp mills. The associated extraction costs can be competitive with conventional forest fuels. However, biofuel extraction reduces the mill\u27s potential to cogenerate electric power. This reduced power output must be compensated by increased purchased power from the grid, with associated costs and emissions. Such emissions must be affected to the extracted biofuel, which cannot therefore be considered as CO2 neutral. This paper presents results for costs and associated greenhouse gas emissions for excess biofuel extracted from a pulp mill. The results show that the extraction costs are competitive, but that the greenhouse gas emissions associated with the exported biofuel can be significant and must therefore not be neglected

Holistic methodological framework for assessing the benefits of delivering industrial excess heat to a district heating network

In Sweden, over 50% of building heating requirements are covered by district heating. Approximately 8% of the heat supply to district heating systems comes from excess heat from industrial processes. Many studies indicate that there is a potential to substantially increase this share, and policies promoting energy efficiency and greenhouse gas emissions reduction provide incentives to do this. Quantifying the medium and long-term economic and carbon footprint benefits of such investments is difficult because the background energy system against which new investments should be assessed is also expected to undergo significant change as a result of the aforementioned policies. Furthermore, in many cases, the district heating system has already invested or is planning to invest in non-fossil heat sources such as biomass-fueled boilers or CHP units. This paper proposes a holistic methodological framework based on energy market scenarios for assessing the long-term carbon footprint and economic benefits of recovering excess heat from industrial processes for use in district heating systems. In many studies of industrial excess heat, it is assumed that all emissions from the process plant are allocated to the main products, and none to the excess heat. The proposed methodology makes a distinction between unavoidable excess heat and excess heat that could be avoided by increased heat recovery at the plant site, in which case it is assumed that a fraction of the plant emissions should be allocated to the exported heat. The methodology is illustrated through a case study of a chemical complex located approximately 50 km from the city of Gothenburg on the West coast of Sweden, from which substantial amounts of excess heat could be recovered and delivered to heat to the city\u27s district heating network which aims to be completely fossil-free by 2030