A chemical engineering firm carries out a Life Cycle Assessment (LCA) to compare the environmental impacts of producing 1000 paper bags versus 1000 low-density polyethylene (LDPE) plastic bags. The key data obtained is shown in the table below:
LCA Metric (per 1000 bags)Paper BagLDPE (Plastic) BagRaw material sourceRenewable (wood)Non-renewable (crude oil)Energy required to manufacture (MJ)2620760Freshwater consumed (litres)4000120Sulphur dioxide emissions (kg)9.51.5BiodegradabilityYesNo \begin{array}{|l|c|c|} \hline \textbf{LCA Metric (per 1000 bags)} & \textbf{Paper Bag} & \textbf{LDPE (Plastic) Bag} \\ \hline \text{Raw material source} & \text{Renewable (wood)} & \text{Non-renewable (crude oil)} \\ \hline \text{Energy required to manufacture (MJ)} & 2620 & 760 \\ \hline \text{Freshwater consumed (litres)} & 4000 & 120 \\ \hline \text{Sulphur dioxide emissions (kg)} & 9.5 & 1.5 \\ \hline \text{Biodegradability} & \text{Yes} & \text{No} \\ \hline \end{array} LCA Metric (per 1000 bags)Raw material sourceEnergy required to manufacture (MJ)Freshwater consumed (litres)Sulphur dioxide emissions (kg)BiodegradabilityPaper BagRenewable (wood)262040009.5YesLDPE (Plastic) BagNon-renewable (crude oil)7601201.5NoBased on this LCA data and environmental chemistry principles, which of the following is the most valid conclusion regarding product selection and process optimization?
Paper bags are unambiguously the more sustainable choice because they utilize a renewable resource and decompose completely under landfill conditions without releasing greenhouse gases.
LDPE bags have a lower overall environmental footprint at every stage of their life cycle (extraction, manufacture, use, and disposal), making them the superior choice in all circumstances.
Although paper bags utilize a renewable raw material, their manufacture is far more energy- and water-intensive than LDPE bags, and their anaerobic degradation in landfills can produce methane, meaning a holistic process improvement must balance resource renewability against manufacturing efficiency and disposal conditions.
To minimize both sulphur dioxide emissions and energy consumption, the company should shift entirely to paper bags, as paper processing uses only mechanical energy and releases no acidic gases.
81 exam-style questions on OCR GCSE Chemistry Improving processes and products. Each one has a worked solution and a mark scheme showing where the marks go.