Cretus researchers from the department of Soil Science and Agricultural Chemistry, Mª Teresa Barral and Remigio Paradelo, have recently published an study on the transfer of heavy metal to crops for human and animal consumption from compost of organic fraction of urban waste.

In their latest work (Heavy metal uptake of lettuce and ryegrass from urban waste composts) they studied the transfer of heavy metals from compost to plants in an experiment with Italian lettuce and ryegrass, grown in substrates based on five urban waste composts rich in metals (Cu, Pb, Cd and Zn), with a manure vermicompost as a comparison.

After cultivation of these two species on both substrates under the same conditions, it was observed that the concentrations of heavy metals do not exceed the maximum content established for foodstuffs in the legislation, even when the concentration in the compost was high. This indicates that the risk associated with the entry of heavy metals into the food chain is very low, especially in the case of lead, even in the case of using large amounts of compost as a soil amendment. However, factors such as pH must be taken into account, as the bioavailability of metals increases with acidic pH.

The findings of the study are of particular importance in the current context, where the intensification of urbanisation implies an increasing production of waste that needs to be properly managed. The composting of the organic fraction of this waste, associated with the use of compost produced as a soil amendment, contributes simultaneously to improving the management of urban waste and combating the degradation and loss of carbon from agricultural soils.

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