Agriculture Reference
In-Depth Information
BREAKDOWN OF ANIMAL, VEGETABLE, AND URBAN
INDUSTRIAL ORGANIC WASTES BY EARTHWORMS
There has been extensive research in the U.K. into the use of earthworms to break down various
animal manures, such as pig and cattle solids and slurries; wastes from laying chickens, broilers,
turkeys, and ducks; horse manure; and rabbit droppings (Edwards 1983). This research at Rothamsted
Experimental Station, Harpenden, Herts, was extended later to studies using earthworms to break
down vegetable wastes, including those from the mushroom industry, processed potato industry,
brewery industry, paper pulp, food wastes from supermarkets, and yard wastes, including grass
clippings and leaves. This work began as a fundamental, interdisciplinary research program on a
laboratory and greenhouse scale, from 1981 to 1985, and involved many biologists, engineers, econ-
omists, and commercial organizations. It was extended to large-scale developmental research on a
Ýeld scale, development of appropriate engineering technology, and eventual commercialization.
This U.K. research had two main aims. The Ýrst was to convert animal and vegetable wastes into
useful soil amendments that could be added to agricultural land to improve soil structure and fertility
or be marketed for horticultural use as a bedding plant growth medium or a component of commercial
potting growth media. The second was to assess the potential of harvesting earthworms from the
earthworm-worked wastes and processing them into a protein supplement to feed Ýsh, poultry, or
pigs. To accomplish these aims, a complex network of interdisciplinary collaborative research was
initiated that involved six research stations, six university or college departments, and eight commercial
organizations. The following main areas of research and development were involved:
1.
A laboratory screening program into the suitability of Ýve different earthworm species
in processing 10 different organic waste materials. The aim was to assess their biological
and economic potentials and study the biology and ecology of these worms in different
organic wastes (Edwards 1988).
2.
Studies to assess the source of nutrition of those species of earthworms that live in
organic wastes; to identify the relative importance of bacteria, protozoa, fungi, and
nematodes in their diet; and to conÝrm which microorganisms are essential to their
survival (Edwards and Fletcher 1988; Morgan 1988).
3.
Evaluation of the rates of conversion of different organic wastes into earthworm biomass
in relation to type of organic wastes, earthworm stocking rates, and effects of environ-
mental factors, especially moisture and temperature (Edwards et al. 1985) (Figure 18.1).
1.0
Total
biomass
(g)
0.8
0.6
0.4
0.2
1:64 1:16 1:8 1:4
1:128 1:32
Stocking rate: weight worm/weight waste
FIGURE 18.1
Optimum stocking rates with
E. fetida
for maximum biomass production.
