FR2236814A1 - Organic-mineral fertilisers produced from bark - by grinding, grading, swelling with steam, drying and screening - Google Patents

Abstract

New natural organic-mineral fertilisers based on dried ground and graded tree bark are produced by (a) stripping off the bark, either manually or mechanically (b) stacking the bark on a moisture-protecting support; (c) grinding down the bark and eliminating impurities, pref. in a mill with graded sieves; (d) swelling the resulting powder by counter-current contact with steam at >=90 degrees C to break down vegetable binders, liberate trace elements and promote microbial growth; (e) drying the powder to a moisture content of 20-25%; and (f) screening the powder in a sieve arrangement providing >=3 different grain size ranges. The powder can be enriched with mineral salts during stage (d). In a variant the bark can be pulped in a conventional wood pulping machine (with recycle of water to avoid loss of trace elements) and formed into thick sheets, when can be ground down when required for use. The fertilisers can be used in horticulture, agriculture, tree nurseries, mushroom growing, etc. They have a high nutrient content (cf compost etc) and contain no pathogenic germs (cf. animal manure). They can be adapted to the acidity of the soil, i.e. coniferous bark (mildly alkaline) for acid soils and deciduous bark (acid pH) for alkaline soils.