Co-utilization of rock dust, mineral fines and compost
Robin A.K. Szmidt & John Ferguson
This report examines the relevance and potential of techniques using rockdust to remineralize soils in Scotland. Rockdust (RD) is a generic term applied to fine materials produced as by-products of quarrying and mineral processing. The concept is concerned with making available a multitude of minerals from freshly crushed rocks that are considered by advocates not to be present in larger quantities in weathered soils. Claimed benefits include :
•enhanced long term sustainable soil fertility and diverse soil biology;
•multi-season effects; •enhanced plant establishment, growth and vigour;
•compatibility with organic farming practices; •enhancement of flavour, aroma and shelf-life of produce;
•high dry matter content, drought resistance, nutritional value and some plant disease resistance of plants;
•in compost, increases in process performance with integrated resource use and
•carbon sequestration by calcium and magnesium carbonate formation, microfloral accumulation and C-accumulation as soil and crop biomass.
Limited research has been undertaken to prove these claims in a Scottish context but there is now a body of evidence that is outlined in this report which overall implies that the use of RD can contribute to the Scottish environment, soil sustainability, national agricultural productivity and assist in meeting targets such as those for recycling and the mass-balance of industrial carbon through sequestration. Health benefits in terms of quality of food, particularly fruit and vegetables are also considered. In Scotland there are already a number of key individuals and resources capable of developing the concept through research and dissemination and the expansion of this resource is proposed. A 19-point prioritised development programme is proposed, with emphasis on education and dissemination and key developments required in:
Carbon life-cycle analysis and sequestration studies;
Minimising fertilizer use by incorporating RD techniques into conventional and organic agriculture;
Assessing optimum plant / RD-type and user conditions;
Assessing long-term dietary benefits associated with mineral content of crops from RD-amended soils Holistic resource use through GIS and cost-benefit analysis of RD-associated industries.
Regulatory issues such as waste management conditions are discussed including a need to review the current BSi PAS100 compliance of RD-amended composts.