LCI

Life Cycle Assessment of PVC

Life cycle assessment (LCA) is a method to quantitatively evaluate the environmental impact (resource and energy consumption, CO₂ emissions, and other environmental negative impact substances) of a product or service throughout its life cycle, from the extraction of raw materials to production, use, and disposal. There is an increasing awareness of the importance of environmental protection and the impact of manufactured and consumed products. We are actively working on calculating this LCA data.

The various environmental impacts quantified by the LCA method, such as the resources consumed, energy consumption, and CO₂ emissions at each stage of a product or service's life cycle (manufacturing, use, and disposal), are called life cycle inventory (LCI). In order to conduct life cycle assessment correctly, it is important to prepare and provide appropriate LCI data.

1. PVC is a material with low energy consumption and environmental impact:

According to comparative data compiled by the Plastic Waste Management Institute on the LCI of 4 major resins in Japan, the process energy from oil extraction to the resin manufacturing stage is 22.3 to 30.0 MJ/kg, with no significant difference between various resins. However, in terms of resource energy, while resins that are mainly made up of hydrocarbons from petroleum are 45.6 to 46.5 MJ/kg, PVC, which contains more than half of its weight in chlorine, is 21.3 MJ/kg, less than half of other resins, indicating a low impact. The total energy impact of PVC processes and resources (46.1 MJ/kg) is 64% of that of low-density polyethylene (LDPE) (72.2 MJ/kg), which is often used in packaging materials, making PVC resin an excellent material with the lowest energy impact. (Figure 1, top)

Looking at the environmental impact of PVC resin, CO₂ is 1.45kg/kg, NOx is 2.43g/kg, and SOx is 2.17g/kg. CO₂ is generally lower than other major resins, and NOx and SOx in particular are at the lowest levels among 4 major resins. (Figure 1, bottom)

図1．汎用樹脂製造のLCIデータ

2．GHG emissions during the processing stage of PVC products are generally small: LCI data for PVC pipes and agricultural films

Typical PVC products include PVC pipes and agricultural films are most typical PVC products. Using the LCA method, the greenhouse gas (GHG) emissions of these primary processed products were calculated.

PVC products are manufactured using polyvinyl chloride resin as the main raw material. The monomer, which is the raw material for polyvinyl chloride resin, is synthesized from ethylene and chlorine. Ethylene is manufactured from naphtha obtained after petroleum refining, and the starting raw material is crude oil. Meanwhile, chlorine is a by-product of electrolysis equipment that manufactures sodium hydroxide, and the starting raw material is industrial salt.

The manufacturing flow (system boundary) from the raw material procurement stage to the manufacturing of PVC products is as shown in Figure 2.

図2．塩ビ製品の製造フロー（システム境界）

The GHG emissions calculated using the LCA methodology up to the manufacturing stage of PVC products are 1.67kg-CO₂eq/kg for PVC pipes^*1） and 2.56kg-CO₂eq/kg for agricultural films (as of November 2021).

図3．塩ビ加工製品のLCIデータ

システム境界：原料調達～樹脂加工まで

• 原料調達〜原料製造段階
• 樹脂加工段階（輸送含む）

The energy consumed in plastic molding processing is mainly due to electricity, and GHG emissions also depend heavily on the amount of electricity consumed. However, the main energy used is different between extrusion and calendaring. Extrusion processing (PVC pipes) mainly uses electricity, while calendaring (agricultural film) uses steam to a large extent as a heat source, and this difference results in different GHG emissions.

In general, with plastic products, as the data in Figure 3 shows, the GHG emissions from processing resin into plastic products are much smaller than the GHG emissions from producing the raw resin.