Not many​ Edinburgh residents collect beach-cast seaweed, but when a winter storm leaves a strandline deposit on Portobello beach, it feels to me like a gift or a visitation from another world. Seaweed has a wonderful benthic weirdness; it’s so rubbery and alien, yet when you add it to the compost heap it becomes velvety, almost ambrosial. In the 17th century, fistfights would break out on the Forth foreshore over who had the right to collect ‘sea-ware for manuring the ground’. These days rotting kelp and bladderwrack are less sought after. People expect a clean beach, so every week the council combs the sand with a tractor and a mechanical surf rake. The resulting harvest is riddled with plastic – wet wipes (polyester or polypropylene), drinks bottles (polyethylene terephthalate) and assorted marine litter – so it gets dumped in landfill. The cost of a clean beach is paid in greenhouse gas emissions, and in reduced foraging for shorebirds like the turnstone, which has been on the UK amber list since 2015. I often try to claim my share ahead of the council tractor, filling a four-wheeled cart that I pull by hand. I use an implement that in Scotland is traditionally called a ‘graip’ and resembles the pitchfork in Grant Wood’s American Gothic. I prefer to work in darkness: there are fewer questions that way. One weekend afternoon when I was straining with 100 kg of kelp along the promenade, someone stopped to ask: ‘Are you gonnae eat that?’ The ingredients of compost are dead things or, as the YouTube gardener Bruce Darrell put it, ‘anything that was recently alive’. I like this definition. Making compost is often beset with prohibitions – you’re not supposed to add meat or dairy or citrus or cooked foods or fish or perennial weeds or bones or rhubarb leaves or diseased plants – and there can be good reasons for these exclusions, from discouraging rats or pathogens to the fact that some things take too long to break down. But what’s the worst that can happen? I now ig