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issue 02/2021

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  • Balance
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Highlights: Injection Moulding Basics: Mass Balance

Basics The Mass Balance

Basics The Mass Balance Approach By: Harald Kaeb, narocon and Michael Thielen T his article is based on a comprehensive new report published by nova-Institute, titled “Bio-based Naphtha and Mass Balance Approach” [1] Climate protection, reduction of greenhouse gas emissions, and saving of fossil resources are key elements for a more sustainable future. The use of renewable feedstocks in historically solely fossil-based chemical processes can contribute to meet these challenges [2]. The chemical industry uses a small number of raw materials to create tens of thousands of different products. The lion’s share of chemical production starts in a cracker, where naphtha, a long-chain hydrocarbon, is split or cracked into smaller molecules. These molecules then serve as the building blocks for downstream production. They include, for example, hydrogen, methane, ethylene, and propylene, which are mainly processed into plastics, coatings, solvents, and crop protection products [3]. Mass Balance is one of several well-known chain of custody approaches which can be used to trace the flow of materials through the value chain resulting in associated claims [2]. The term Mass Balance in general describes a “Relationship between input and output of a specific substance within a system (defined by boundaries) in which the output from the system cannot exceed the input into the system” [4]. One of the most applied and known cases in practice is the system “renewable energy in the electric grid”. Energy is generated by a photovoltaic, wind turbine or hydropower system, and an exactly known input (energy equivalent in kwh) is supplied to the electric grid. The output is allocated to a user buying 100 % renewable energy, whilst in fact the energy of the grid comes from various sources including high percentages of fossil energy [3]. In chemical and plastics systems, the Mass Balance approach is about carbon-based feedstocks used as input and a defined interim or end-product as output. The system typically is a huge chemical hub with various synthesis routes and processes grouped around a central element: the thermochemical cracker. Those hubs have been built in many places of the world, and a huge share of organic chemicals (bulk chemicals are ethylene, propylene, butylene, aromatics) and industrial carbon-based products come from cracker-based chemistry (e.g., >90 % of the global polymer supply, i.e. PE, PP, PVC, PET, but also most of the PA, PUR, ...) [3]. The main feedstock for the traditional organic “cracker chemistry” is naphtha, a fraction of crude oil refining. Today, fractions with very similar chemical composition and behaviour, which are derived from renewable or recycled feedstock, can substitute fossil feedstocks in crackers. The biobased feedstock alternative is often called “bio-naphtha”, made from a by-product of biodiesel (hydrogenated vegetable oils (HVO), either from plants or from food waste, such as waste cooking oil). Another viable option to sustainable feedstocks used in such installations is a mix of biobased, CO 2 -based, and recycled feedstocks, recently also summarised under the term renewable carbon. So, when applying the Mass Balance approach, the renewable or recycled feedstock added at the beginning of the production process is later allocated to the end product. However, this way of mathematically allocating the feedstock to the end product needs a high level of trust. One key element, the rules for allocation, is less simple to define and be agreed-on by a broad stakeholder community than it may look at first glance. What is allowed, scientifically sound, verifiable, and safe, has been discussed by several players and platforms in past years. Part of it is about setting the right boundaries, avoiding double accounting, and embedding the method in LCA. Different certifying bodies, such as ISCC plus, TÜV/DIN Certco, RSB, or REDcert, offer certification schemes. But with no ISO or EN standard in place yet, the current situation can only be described as at least partly confusing and cloudy. But a standardisation of the Mass Balance approach under the umbrella of the horizontal standard ISO 22095 “Chain of Custody – General Models and Terminology” is now underway. The working group ISO/PC 308 organises sessions on two future standards on Mass Balance and Book and Claim. The methodology and rules will apply for both chemical recycling and biobased content Mass Balance. At the end of the day the concept of Mass Balance will allow that feedstocks switch from fossil to renewable, from virgin fossil to (plastic) waste – or to CO 2 chemistry. Therefore, the Mass Balance approach is not an option, a nice to have: it is a fundamental need of the future circular bioeconomy. The establishment of chemical recycling is indispensable without Mass Balance Approach, because there is no other way to determine inputs (plastic waste) and outputs (recycled polymers) in a trustful and proper way. The situation today is like with chemistry before it grew big on oil and gas, more than 100 years ago. It will now need to change to renewable and sustainable feedstocks to a large extend within the next 20–30 years, to help fighting the climate emergency and give future societies the opportunity for a good life. Material-based carbon emissions make up almost half of the total emissions of the German chemical industry [5]. The full report [1], which also features a chapter on bio-based naphtha (by Doris de Guzman) and one about standardisation of the Mass Balance approach (by Michael Carus) is available for sale at Harald Kaeb shows in his chapter the already many examples of biobased polymers and products based on mass balance approach. 52 bioplastics MAGAZINE [02/21] Vol. 16

Basics References [1] Carus, M.; de Guzman, D.; Kaeb, H.: Bio-based Naphtha and Mass Balance Approach Status & Outlook, Standards & Certification Schemes, Report, nova Institute, Hürth, Germany, March 2021, [2] N.N.: Mass Balance Approach to accelerate the use of renewable feedstocks in chemical processes. PlasticsEurope (Ed.), 2020-01-29; file/force/3390/315 [3] N.N.: The Mass Balance Approach, ( [4] N.N.: European Commission 2018: Knowledge for policy – Mass balance. Last access 2021-03- 03. [5] N.N. VCI Roadmap 2050 Info See a video-clip at: massbalancevideo Principle of Mass Balance Approach (nova-Institute) Brand-Owner’s perspective on bioplastics and how to unleash its full potential Brand-Owner “As a product packaging and tableware producer for the foodservice and travel market, our product innovation strategy is strongly built around moving towards a circular economy. We follow the principles of the Ellen Mac Arthur Foundation to achieve our 2025 targets to have all our products ready to fit into the circular economy and we have undersigned the Global Commitment of the UN Global Tourism Plastic Pact to increase the sustainability of our plastic usage. We believe that packaging materials need to circulate in closed loops by reusing, recycling, or composting the raw materials. Reusable packaging is a market that is expected to grow strongly in the coming years. These reusables require durable and easily recyclable materials to fulfil their purpose. Bioplastics will be instrumental in decoupling the circular materials from fossil feedstock and replacing them with the right renewable resources. The bioplastics that meet these requirements will allow us to leverage all the benefits of plastics while avoiding the downsides that have provided them with a bad image.” Pieter Willot, Sustainability Manager at deSter, a gategroup member | bioplastics MAGAZINE [02/21] Vol. 16 53

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