Cylinder head remanufacturing
utilizing gas fusion welding
89.4% Saving on Carbon Emissions
1. Introduction – Life cycle assessment of potential environmental impact reductions
In the last few decades, global environmental sustainability concerns have steadily increased due to climate changes, creating important and serious challenges to the transport sector and especially the maritime industry. Many studies indicate, that transitioning towards a circular economy may serve as key strategies to mitigate such challenges.
Circular economy creates value for businesses while minimizing environmental impacts and resource consumption through system-thinking by implementing strategies redefining products, product systems, and services. As an example, redefining a product system from a conventional linear approach to a circular approach, extending a product’s lifespan, may prove both economically and environmentally beneficial. From an economical perspective, life extension strategies introducing a circular loop may reduce the cost from investing in new products or other factors related to the product system significantly. From an environmental perspective, life extension strategies may reduce the environmental impacts significantly, from e.g. manufacturing of a new product, by keeping the product in a circular loop thus avoiding the need for a new product. (PRé Sustainability, 2020).
To evaluate the environmental impacts, and thereby to evaluate circular economy, life cycle assessment is a beneficial tool to quantify impacts strengthening the propositions of circular economy. Life cycle assessment is defined as a robust science-based tool to measure impacts from implementing circular strategies, product changes, and new business models. Life cycle assessment complements circular economy in a three-step way by enable the ability to test the assumption of circular economy business models on a product or system level, identifying and recognising limitations of the circular model. Furthermore, it investigates new and alternative approaches and setting objectives to continuously improve circularity for practical implementation at business level (PRé Sustainability, 2020).
In technical terms, life cycle assessment is an international standardised method to quantify and estimate the use of resources, emissions, and environmental and health impacts related to a product or system. Depending on the scope and type, the life cycle assessment may consider the entire life cycle of a product or system, including resource extraction, production of raw materials, production or manufacturing of the product, use of the product, maintenance of the product, and end-of-life processes such as disposal, recycling, incineration, landfill etc. Life cycle assessment is a key tool to identify environmental impacts, either by single product investigation or by comparative studies, to evaluate carbon footprint or to avoid burden shifting, thus defining it as a crucial decision-support tool when implementing circular strategies and thereby addressing sustainability. The life cycle assessment framework is defined by the ISO 14040 and 14044 standards which specifies the standardised assessment procedure for practitioners to follow. However, these standards allow for several choices that may affect the legitimacy of the assessment outcome, which has resulted in the development of the International Reference Life Cycle Data System (ILCD). The ILCD works as a guidance for consistent and quality assured life cycle assessments and data outcomes, coordinated by the European Commission, and acts as template for good-practise life cycle assessments. The ISO/ILCD approach is followed in this project to ensure consistent and accurate assessment outcome, complying with the European Commission recommendations.
The ISO/ILCD approach divides the project into four assessment steps adapted from the ILCD framework:
- Goal definition
- Scope definition
- Inventory analysis
- Impact assessment
The goal definition addresses the intended application of the assessment, method assumption and limitations, the reason for the assessment and its decision context, target audience, the involvement of comparative assessments, and the commissioner of the assessment and possible influencing factors. The scope definition defines the assessment by addressing the form and types of deliveries, the object of assessment, the chosen life cycle inventory analysis modelling framework and correlating multifunctional processes, system boundaries, the basis for impact assessment e.g. which impact categories to include, and the technological, temporal and geographical representativeness of the assessment.
The inventory analysis is the process where the product system is modelled, and elementary flows are gathered for all processes in the system and scaled in accordance with the reference flow of the assessment.
The impact assessment is the phase where the inventory and elementary flows are modelled resulting in an output identifying the contribution to each individual impact category at midpoint or endpoint level. Often, the robustness of the model is evaluated against a set of sensitivity checks, identifying parameters potentially sensitive to changes thus altering the outcome of the model. The impact assessment consists of five elements, translating the elementary flows of the inventory into potential contributions to different impact categories. The first element is the selection of impact categories and category indicators laying the basis for the impact assessment. For further modelling and calculation of environmental impact contributions to each impact category, a characterisation method should be chosen in the life cycle modelling software to calculate the characterised impact scores e.g. carbon footprint. The characterised impact scores are then normalised and weighed to support comparison across impact categories.
The last part of the life cycle assessment is the interpretation and conclusion, and further recommendations. The conclusion sums up the assessment, evaluating main findings from both early and late phases of the assessment in accordance with the goal and scope definition. Potential limitations to the assessment are drawn from the conclusion which leads to the development of recommendations to the targeted audience also in accordance with the goal and scope definition and the intended application of the assessment.
This introduction was mainly based on the literature found in ILCD Handbook, 2010 and the ISO 14040 and ISO 14044, respectively.
6. Life Cycle Conclusion
The intended application of this life cycle assessment was to quantify the potential environmental impact reductions related to the Cast Iron Welding Services UK cylinder head remanufacturing when incorporated in the business-as-usual life cycle of the cylinder head, with emphasis on carbon footprint. The assessment aimed at investigating the environmental impacts related to the production of subcomponents, manufacturing and assembly of the cylinder head, the Cast Iron Welding Services specific cylinder head remanufacturing prolonging its life cycle hence avoiding the manufacturing of a new cylinder head, and the end-of-life disposal of the cylinder head, by comparing the life cycle impact assessment of a business-as-usual scenario and a Cast Iron Welding Services remanufacturing scenario comparing the environmental impacts from each scenario.
From the impact assessment of the business- as-usual cylinder head life cycle scenario, a carbon footprint of 7,752 kg CO2 eq. was calculated. Implementing a circular strategy in the business-as-usual scenario, such as the Cast Iron Welding Services remanufacturing process, proved to have a carbon footprint reduction potential of 89.4%, reducing the total life cycle carbon footprint from 7,752 kg CO2 eq. to 824.4 kg CO2 eq. by avoiding the manufacturing of a new cylinder head hence keeping the resources in a circular loop. The large reduction potential is found in the manufacturing stage of the cylinder head. Assessing all direct and indirect emissions related to the manufacturing stage, a carbon footprint of 7,601 kg CO2 eq. per cylinder head is calculated including all manufacturing activities, cylinder head subcomponents, auxiliaries, and transportation scenarios. In addition, the total carbon footprint including direct and indirect emissions for the Cast Iron Welding Services remanufacturing life cycle stage was calculated yielding a carbon footprint of only 684 kg CO2 eq. per cylinder head not including the reduction from the avoided output to the technosphere (new cylinder head). Comparing these two life cycle stages, with a remanufactured cylinder head substituting the manufacturing of a new one, it underlines the significant carbon footprint reduction potential from choosing a circular strategy such as remanufacturing even if the remanufacturing process is energy- or material intense.
To test the robustness of the model, five scenarios was chosen for sensitivity analysis altering specific parameters in the remanufacturing life cycle stage which was assumed to be potential variables. The five scenarios for the sensitivity analysis was as follows: 20% increase in electricity use, 20% decrease in electricity use, steel cast iron welding rods instead of nickel cast iron welding rods, remanufactured cylinder head lorry transportation to Italy instead of sea freight to Philippines, and a life cycle inventory modelling framework change to test modelling outcome robustness. The first sensitivity analysis assumed a theoretical 20% increase in the electricity usage for the remanufacturing process hence calculating a total carbon footprint reduction change from 89.4% to 89.0% or from 824.4 kg CO2 eq. to 850.0 kg CO2 eq. proving no sensitivity for any impact categories in the impact assessment model. The second sensitivity analysis assumed a theoretical 20% decrease in the electricity usage for the remanufacturing process hence calculating a total carbon footprint reduction change from 89.4% to 89.8% or from 824.4 kg CO2 eq. to 790.8 kg CO2 eq. proving no sensitivity for any impact categories in the impact assessment model. The third sensitivity analysis assumed the use of steel cast iron welding rods instead of nickel cast iron welding rods hence calculating a total carbon footprint reduction change from 89.4% to 94.1% or from 824.4 kg CO2 eq. to 729.6 kg CO2 eq. proving sensitivity for 5 out of 16 impact categories in the impact assessment model, but not for the carbon footprint impact indicator. The fourth sensitivity analysis assumed a theoretical change in the transportation scenario, transporting the cylinder head to Italy instead of the Philippines, hence calculating a total carbon footprint reduction change from 89.4% to 90.4% or from 824.4 kg CO2 eq. to 746.4 kg CO2 eq. proving no sensitivity for any impact categories in the impact assessment model. The last sensitivity analysis was made for testing the life cycle inventory modelling strength to evaluate if other types of modelling frameworks would alter the impact assessment outcome significantly hence calculating a total carbon footprint reduction change from 89.4% to 89.2% or from 824.4 kg CO2 eq. to 835.2 kg CO2 eq. proving no sensitivity for the carbon footprint impact category in the impact assessment model.
From the comparative life cycle assessment of the 1200 kg cylinder head and the Cast Iron Welding Services remanufacturing process as a circular strategy to extend the lifespan of the cylinder head it can be concluded that changing the linear life cycle to a circular life cycle, remanufacturing the cylinder head to prolong its lifespan, may prove beneficial in regards to significant carbon footprint reductions and thus supporting a sustainable transition in the maritime industry. Furthermore it can be concluded, that significant carbon footprint reductions may be obtained should the remanufacturing process require extensive energy to complete thus underlining that remanufacturing should be chosen as the primary strategy for prolonging the lifespan of a cylinder heads to reduce carbon footprint in the maritime industry.
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Appendices provided separately and only online.
Complete life cycle assessment modelling: Characterised, normalised, and weighted result
Life cycle inventory analysis