The vinegar solution was tested on groundwater tainted by former textiles factories, smelters, and tanneries. The leftovers of these industries produced harmful chromium compounds that cause cancers and all kinds of kidney, liver, lung and skin troubles. But add dilute acetic acid, aka vinegar, and—presto!—the oxidized chromate became non-soluble. That means it's no longer bio-available and can be left safely in the ground without risk to the surrounding ecosystem. The vinegar feeds and grows naturally-occurring bacteria which then alter the chemistry of the chromium compounds, rendering them harmless.
Good job bacteria!
The chicken guano solution was used on soil contaminated by crude oil spills. Conventional clean-up bears a heavy environmental cost since detergents become pollutants themselves and persist in the environment for a long time. Better to bioremediate: use natural or engineered microbes to metabolize the organic components of crude oil. But too often that requires expensive nitrogen and phosphorus fertilizers with their own hefty environmental price tags (decreased soil quality). But when chicken manure was added to the soil—presto!—nearly 75 percent of the oil was broken down after two weeks. At least 12 different species of oil-munching bacteria liked the chickenshit menu and responded by metabolizing the oil.
Let's dig back through our great-grandmothers housekeeping diaries and find out what else they (probably) knew that we've forgotten?