How we weigh.

Every product in the archive is broken down into its component parts, bottle, cap, pump, label, adhesive, and weighed against industry-standard container measurements. No weight rests on a single study: container masses are cross-checked against two independent packaging life cycle assessments, and closures, pumps and sprays against a third that measures dispensing systems part by part. Beverage bottles are checked against European PET industry data, flexible film against published film grammages, and garments against a public life cycle study that weighed real retail items. Recyclability is estimated using national MRF acceptance rates for the polymer involved. Persistence windows follow four peer-reviewed studies: Chamas et al. (2020) for degradation rates, Min et al. (2020) for how thickness and crystallinity change them, Beltrán-Sanahuja et al. (2020) for measured mass loss in seawater, and Redko et al. (2024) for polyethylene excavated after up to sixty years in a landfill.

Weights are averages, not single-brand audits. A specific product on your shelf may differ by ±15%. Material chemistry, color additives, and label adhesives often determine recyclability more than the polymer itself. Persistence figures are modelled ranges, not measured end dates, and we now publish them as ranges everywhere. Each item is placed in one of four windows by format, because measured degradation rates scale with wall thickness rather than with brand: thin film, wrappers and bags 20 to 200 years, thin rigid items such as cups, tubes and cutlery 100 to 400 years, bottles, jars and rigid containers 200 to 600 years, thick rigid items and hard shells 400 to 1,000 years. The bands follow Chamas et al. (2020), with Min et al. (2020) and Gewert et al. (2015) for polymer differences and Napper and Thompson (2019) for films. We deliberately avoid the widely repeated claim that a plastic bottle takes 450 years to break down, because that number cannot be traced to any measurement, as Ward and Reddy (2020) set out.

Production footprint

Each item also carries an estimate of the water and electricity required to manufacture the packaging, not to use the product. We apply cradle-to-gate resin figures of roughly 0.009 litres of blue water and 0.003 kWh of process electricity per gram of PET, HDPE, or PP, plus a small fixed overhead for filling and labelling. Those coefficients come from the Franklin Associates cradle-to-gate assessments for the American Chemistry Council (8.1 litres per kilogram for HDPE, 9.1 for PP), the PlasticsEurope Eco-profiles, and the peer-reviewed polymer water-footprint study by Korol et al. (2019). Total primary energy including feedstock is far higher, around 20 to 25 kWh per kilogram, but that is not electricity and we do not present it as such. Figures are per unit, not per use, and are intended as order-of-magnitude estimates.

Industry data

Some of our best engineering figures come from industry associations: NAPCOR and Petcore Europe for bottle masses, PlasticsEurope for resin datasets, the U.S. Plastics Pact for tube composition. We use them, because nobody measures packaging more precisely than the people who make it, but we treat them as interested parties. Recyclability, recycling rates and recycled content are contested figures, so an industry number is never allowed to stand alone there: it is read next to peer-reviewed or institutional evidence, and where no independent equivalent exists we say so on the source itself. Industry sources are marked as such on the Sources page.

Source: industry container averages, public packaging audits, and peer-reviewed and institutional life cycle assessments listed under Sources.