Recycling campaigners and environmental groups often quote alarming statistics on how much waste one person produces each year. But a comprehensive report on rubbish collected in New York City throughout the twentieth century claims that the figure has dropped dramatically, from its peak in the 1940s.

Writing in Environmental Science and Technology (doi: 10.1021/es011074t), Daniel Walsh describes the rise and fall of garbage components in the Big Apple. Using the most complete set of municipal records for a US city's residential refuse, Walsh records a maximum output of 940 kg of waste per person in 1940, and a low of 320 kg per person in both 1961 and 1963.

Surprisingly, since the 1980s a person's annual throwaways have stabilized at a relatively low 430 kg. Also, the most significant trash trends were mostly declines in the percentages of different categories of waste. The relative amounts of fuel ash, food waste, metal and glass dropped, but the percentage of plastics rose and that of paper remained the same. The photograph on the left shows ash collection earlier in the twentieth century; that on the right a present-day scene.

Between 1920 and 1990 there was a 50% decrease in refuse density. Walsh attributes this to a decrease in coal and other fuel ash, and to technologies that have enabled product packaging to switch from glass and metal to paper and plastic. Over the same period, organic-matter waste rose fourfold, increasing the greenhouse-gas potential per unit of dumped or incinerated garbage. Walsh estimates that the totality of New York City's refuse for the past century represents a carbon pool of 80 million tons.

As coal was at the start of the twentieth century, paper is now the most abundant category of refuse, accounting for roughly 35% of all residential discards. Will the figures for the twenty-first century reflect the long-forecast advent of the paperless office?