Brownfield sites: making them green and useful again

Brownfield sites: making them green and useful again September 2, 2023Leave a comment

Why should we be interested in brownfield sites? These are wastelands that have been previously developed and are no longer in use. There are LOTS of them in Europe waiting to accommodate new homes or parkland. And they are much more accessible than increasingly scarce greenfield sites. Why then are they not developed? Because we are all scared off by POLLUTION. There are 1,4M polluted sites in an uncompleted census of the EU (minus Central Europe). Registers in France indicate at least 100,000 ha of polluted sites while those in the UK show enough suitable brownfield land for over a million homes.

These brownfield sites are being cleaned up for development, gradually but surely. Site de-pollution is expensive and slow. The faster you want to clean up a brownfield site the more you have to pay for de-pollution. There is thus a trade-off for developers: get a site cleaned quickly at greater cost but also get a quicker payback for buildings that can be located there that much earlier.

There is also the nature of the pollution to be factored in. This isn’t always known before the clean-up begins and there can be many surprises en route — from medieval artifacts to WW2 graves and unexploded ordinance. Bricks, broken windows and rubble are easy to see and clear, but what lies under them deep in the soil is not. Most soil pollution is petroleum-based or agrochemicals and (relatively) easy to deal with. But nasty stuff (asbestos, dioxins, PCBs, heavy metals, arsenic, pharmaceutical wastes, decomposing mastodons…) can leach into the soil and resist remediation and final disposal.

There are 2 basic depollution processes: “in situ” (on site remediation) and “ex situ” (carting the soil and mastodons elsewhere to treat them). The cheapest of these is in situ and gets mother nature to do all the work: plants growing on the brownfield site remove a lot of the nasties (including heavy metals) into the air via phytoremediation, something that can be enhanced by pointy-headed boffins in white labcoats. Needless to say, even if this is eco-friendly, it takes mastodon years to accomplish.

The most expensive process is ex situ — fast, thorough and not particularly eco-friendly. This is something called thermal desorption that imitates phytoremediation by souping up the process big-time using an external energy source. This is done by rednecks in muddy boots out on the brownfield. In six months, your multi-hectare brownfield site will be cleaned up, the remediated soil replaced and the site ready to be built on. All the nasties will have certifiably entered the atmosphere as harmless compounds and the heavy metals oxidized in a non-soluble form. (The neighbours will also be glad the rednecks have disappeared as this process can be noisy and is often carried out 24/7.)

SAI has been working with the European champion of ex situ thermal desorption for the past 15 years. This is a Finnish company located on the Arctic circle called Savaterra. Over the years its patented process has become more eco-friendly with the use of its own recycled energy. If you have just purchased a derelict gas station and want to build on this brownfield site, don’t call us. We only remediate brownfield sites containing the equivalent of at least 16 mastodons.

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