One Saturday in early June, a group of people gathered behind an old meatpacking plant on Chicago’s South Side, armed with shovels and handmade compost sifters.
In teams of three, the group began sifting a huge pile of rubble excavated from the lot in order to install an anaerobic digester. One person scooped rubble on to the screener, while the other two shook the screen back and forth, forcing small particles through while keeping large rocks and branches out.
“Soil has three components: Sand, silt and clay,” explained soil expert Dominic Brose as the group rested between bouts of sifting. “This is mostly sand we’re getting here. Hardly any clay.”
Soil scientist Dominic Brose explaining soil structure at a Plant Chicago soil-building workshop.
The setting was The Plant, a former meatpacking facility turned urban food hub. The occasion wasOpen Source Circular Economy (OSCE) Days 2015, a worldwide hack-a-thon aimed at inspiring people to reconsider waste, production and the economy as we know it.Because Plant Chicago focuses on urban agriculture and material reuse, we decided to host an OSCE Days workshop with the challenge of building soil from all locally available materials.
We invited Brose, a soil scientist with the local wastewater treatment facility. He brought a 10-cubic yard load of composted wastewater solids (biosolids). We also had a truckload of woodchips dumped on site and set to work creating the sand portion of our soil recipe. With Dominic, a few Plant Chicago staff and six other workshop attendees, we sifted for two hours, yielding about a cubic yard of sand.
Estimating that the lot would need about 500 cubic yards of sand to meet our soil-building goals, we’d obviously need to innovate beyond hand-sifting. We spent the rest of the workshop brainstorming and drawing plans for building our own automated sifting machine from salvaged materials.
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