Table Of ContentProceedings of Previous Easter Schools in Agricultural Science, published by Butterworths,
London
•SOIL ZOOLOGY Edited by D. K. McL. Kevan (1955)
*THE GROWTH OF LEAVES Edited by F. L. Milthorpe (1956)
•CONTROL OF THE PLANT ENVIRONMENT Edited by J. P. Hudson (1957)
•NUTRITION OF THE LEGUMES Edited by E. G. Hallsworth (1958) -
•THE MEASUREMENT OF GRASSLAND PRODUCTIVITY Edited by J. D. Ivins
(1959)
•DIGESTIVE PHYSIOLOGY AND NUTRITION OF THE RUMINANT Edited by D.
Lewis (1960)
•NUTRITION OF PIGS AND POULTRY Edited by J. T. Morgan and D. Lewis (1961)
•ANTIBIOTICS IN AGRICULTURE Edited by M. Woodbine (1962)
•THE GROWTH OF THE POTATO Edited by J. D. Ivins and F. L. Milthorpe (1963)
•EXPERIMENTAL PEDOLOGY Edited by E. G. Hallsworth and D. V. Crawford (1964)
•THE GROWTH OF CEREALS AND GRASSES Edited by F. L. Milthorpe and J. D.
Ivins (1965)
•REPRODUCTION IN THE FEMALE MAMMAL Edited by G. E. Lamming and E. C.
Amoroso (1967)
•GROWTH AND DEVELOPMENT OF MAMMALS Edited by G. A Lodge and G. E.
Lamming (1968)
•ROOT GROWTH Edited by W. J. Whittington (1968)
•PROTEINS AS HUMAN FOOD Edited by R. A. Lawrie (1970)
•LACTATION Edited by I. R. Falconer (1971)
•PIG PRODUCTION Edited by D. J. A. Cole (1972)
•SEED ECOLOGY Edited by W. Heydecker (1973)
HEAT LOSS FROM ANIMALS AND MAN: ASSESSMENT AND CONTROL Edited
by J. L. Monteith and L. E. Mount (1974)
•MEAT Edited by D. J. A. Cole and R. A. Lawrie (1975)
•PRINCIPLES OF CATTLE PRODUCTION Edited by Henry Swan and W. H. Broster
(1976)
•LIGHT AND PLANT DEVELOPMENT Edited by H. Smith (1976)
PLANT PROTEINS Edited by G. Norton (1977)
ANTIBIOTICS AND ANTIBIOSIS IN AGRICULTURE Edited by M. Woodbine
(1977)
CONTROL OF OVULATION Edited by D. B. Crighton, N. B. Haynes, G. R. Foxcroft
and G. E. Lamming (1978)
POLYSACCHARIDES IN FOOD Edited by J. M. V. Blanshard and J. R. Mitchell
(1979)
SEED PRODUCTION Edited by P. D. Hebblethwaite (1980)
PROTEIN DEPOSITION IN ANIMALS Edited by P. J. Buttery and D. B. Lindsay
(1981)
PHYSIOLOGICAL PROCESSES LIMITING PLANT PRODUCTIVITY Edited by C.
Johnson (1981)
ENVIRONMENTAL ASPECTS OF HOUSING FOR ANIMAL
PRODUCTION Edited by J. A. Clark (1981)
EFFECTS OF GASEOUS AIR POLLUTION IN AGRICULTURE AND
HORTICULTURE Edited by M.H. Unsworth and D.P. Ormrod (1982)
CHEMICAL MANIPULATION OF CROP GROWTH AND DEVELOPMENT Edited
by J. S. McLaren (1982)
CONTROL OF PIG REPRODUCTION Edited by D.J.A. Cole and G.R. Foxcroft
(1982)
SHEEP PRODUCTION Edited by W. Haresign (1983)
• The titles are now out of print but are available in microfiche editions
upgrading Waste for Feeds
and Food
D.A. LED WARD, MSc,PhD,FiFST
A.J. TAYLOR, BSC, PhD
R.A. LAWRIE, BSC, Pho, DSC, SCD, FRSE, FRSC, FIFST
University of Nottingham School of Agriculture
BUTTERWORTHS
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Net Books and may not be re-sold in the UK below the net price
given by the Publishers in their current price list.
First published 1983
© The several contributors named in the list of contents 1983
British Library Cataloguing in Publication Data
Upgrading waste for feeds and food.
1. Waste products as feed—Congresses
L Ledward, D.A. Π. Taylor, A.J.
in. Lawrie, R.A.
338.1'6 SF95
ISBN 0-408-10837-1
Library of Congress Cataloging in Publication Data
Main entry under title:
Upgrading waste for feeds and food.
Based on the 36th Easter School in Agricultural
Science.
Bibliography: p.
Includes index.
1. Agricultural wastes—Congresses. 2. Waste
products as feed—Congresses. 3. Food industry and
trade—Congresses. I. Ledward, D.A. II. Taylor,
A.J. (Andrew John), 1951- . III. Lawrie, R.A.
(Ralston Andrew) IV. Easter School in Agricultural
Science (36th : 1982? : University of Nottingham)
TP995.A1U63 1983 664'.096 83-7548
Typeset by Scribe Design Ltd, GiUingham, Kent
Printed and bound by Robert Hartnoll Ltd, Bodmin, Cornwall
PREFACE
It is now many decades since the world was alerted to the possibihty that
the number of human beings might increase beyond the capacity of the
available nutrients to feed them.
There have been, and there wih continue to be, vigorous and successful
attempts by agriculturalists to produce more food, but this is not the only
approach to the problem. Large quantities of nutrients are wasted after
they have been produced because they are unpalatable or because they
have been improperly stored. Moreover, insofar as such waste contributes
to environmental pollution, it is doubly undesirable.
It was the purpose of the 36th Easter School in Agricultural Science to
consider how currently wasted or underutilized nutrients could be reco
vered and upgraded in order to make available more food, either directly
or through animal intermediaries; and to assess what progress had already
been made in seeking a solution to this problem.
The various chapters in this volume are the contributions made at the
School by invited experts. The editors hope that readers will find in this
volume the breadth and depth of coverage necessary to appreciate this
field of scientific endeavour, which is increasingly important and of
concern to all.
ACKNOWLEDGEMENTS
The editors are glad to take this opportunity of acknowledging the
expertize and efforts of all those who contributed papers at the Easter
School.
They are also indebted to the following gentlemen who kindly acted as
session chairmen: Sir David Cuthbertson, CBE, formerly Honorary Presi
dent of the British Nutrition Foundation Ltd; Dr H. Egan, Government
Chemist, 1970-81; Professor R.F. Curtis, Director, ARC Food Research
Institute, Norwich; Dr W.J.F. Cuthbertson, OBE, Consultant, London;
Dr R.B. Hughes, Technical Director, CT. Harris (Calne) Ltd; and
Professor A.E. Bender, Professor of Nutrition, Queen Elizabeth College,
University of London.
The University of Nottingham wishes to express its gratitude for the
generous financial contributions of the following organizations. These
assisted in meeting the costs of bringing overseas speakers to the School.
Albright & Wilson Ltd
Alginate Industries Ltd
Batchelors Foods Ltd
The British Council
The British Petroleum Company Ltd
Imperial Foods Ltd
Pedigree Petfoods Ltd
Pork Farms Ltd
Purina Protein Application Ltd
Seymour, Arthur H. & Son Ltd
Shell Research Ltd
United Biscuits (UK) Ltd
Walkers Crisps Ltd
In conclusion, the editors wish to thank warmly all those members of
staff and students at the School of Agriculture who gave their time in the
interests of the Symposium. The help of Mrs D.M. Borrows, Mrs B.E.
Dodd, Mrs D. Treeby, Mr G. Millwater, Mr P. Glover and Mr J. Rosillo
was particularly appreciated.
VI
1
WORLD OUTLOOK FOR FOOD
DAVID PIMENTEL
College of Agriculture and Life Sciences, Cornell University, USA
and
MARCIA PIMENTEL
Division of Nutritional Sciences, College of Human Ecology, Cornell
University, USA
Introduction
At no time in human history have food shortages been as widespread and
affected as many people as they do today. An estimated five hundred
milHon people in the world are malnourished (NAS, 1977)—and the food
supply problem will become more severe as the world population rapidly
grows from the present level of nearly five thousand million to 12 to 16
thousand million by 2150 (UN, 1973). We know humans must have an
adequate amount of food and that these foods must contain the many
nutrients essential to sustain life. The basic problem then, is how to
provide such a food supply in the face of increasing populations and
diminishing resources needed to produce this food.
Therefore, in planning for the coming decades we need to consider not
only the present conditions affecting food production, but the many
constraints that may impede our achieving these goals in the future. Thus
the interplay among population growth, energy resources, land availabil
ity, water supplies and use of biological wastes needs to be examined.
Only when these interrelationships are clearly understood will we be able
to make viable plans for the future.
World population
For 99% of the time that humans have inhabited the earth, the world
population numbered less than eight miUion (Coale, 1974), and the total
population of North America numbered less than 200000. Now every day
more than 200000 humans are added to our rapidly growing numbers so it
is no wonder the human population is projected to increase to 6.5 thousand
million by the turn of the century. Numerous studies hke that of the
National Academy of Sciences pessimistically state there is no feasible way
to stop the explosive increase of the world population short of some
catastrophe (NAS, 1971). To provide food to feed the rapidly growing
numbers of humans during the next 25 years will require a doubling of
world food supply.
Probably one of the most important factors responsible for the popula
tion explosion has been the escalating use of fossil energy {Figure 1.1).
4 World outlook for food
From 1800 to the early 1970s, fossil energy has been ample in supply and
low in cost. As a result, industries have flourished; agriculture has become
more productive through mechanization, but more dependent on pesti
cides and fertilizers; human disease control operations have been more
successful; and unfortunately military armaments have become more
deadly.
1600 1700 1800 1900 2000 2100 2200 2300 2400
Years AD
Figure 1.1 Estimated world population numbers ( ) from 1600 to 1975 and projected
numbers ( ) (?????) to the year 2250. Estimated fossil fuel consumption (—) from 1650
to 1975 and projected ( ) to the year 2250 (after Pimentel et al., 1975)
Basically, increased food production and more effective control of
human diseases, have contributed most to the alarming growth of world
population (NAS, 1971). Of the two, evidence suggests that reducing death
rates through effective public health programs has contributed the most to
increased population growth (Freedman and Berelson, 1974). For exam
ple, in Mauritius, eradication of malaria-carrying mosquitoes by using
DDT, a fossil-based pesticide*, produced a dramatic reduction in death
rates (PEP, 1955; UN, 1957-1971). In just one year, death rates fell from
27 to 15 per 1000 over a period of five years.
Then, because fertility rates did not decrease, an explosive increase in
population has occurred.
Events in recent history document similar occurrences where medical
technology and availabihty of medical supplies have significantly reduced
*To produce and apply 1 kg of DDT uses about 8€ of oil; 1 kg of DDT provides effective
control for several months in about 70 small homes.
David Pimentel and Marcia Pimentel 5
death rates (Corsa and Oakley, 1971). Based on experience, the inevitable
conclusion is that it is relatively easy to reduce death rates, but birth rates
are difficult to curtail because they are dependent on multidimensional
factors and deeply rooted social customs. Consequently, our efforts must
be focused not only on population control, but must be redoubled to find
ways to augment a nutritious food supply. The latter aim is the focus of this
discussion.
Energy resources for agriculture
Energy use in agricultural production has evolved and changed over the
thousands of years humans have cultivated the earth. As human numbers
increased, many regions could no longer support the primitive hunting-
gathering economy and a shift was made to a more permanent type of
agriculture (Boserup, 1965). 'Slash and burn' or 'cut and burn' agriculture
(i.e. cutting trees and \)rush and burning them on site) was the first
agricultural technology used. Because this practice killed weeds and added
nutrients to the soil, crop production was satisfactory for two to three
years. Then soil nutrients became depleted and about 20 years had to
elapse before the forests regrew and soil nutrients were renewed.
Cut and burn crop technology required an ax and hoe and much
manpower. For example, Lewis (1951) who investigated 'slash and burn'
corn culture in Mexico, reported that a total of 1144 h of labor was
required to raise a hectare (ha) of corn {Table 1.1). Other than human
energy, the only other inputs were the ax, hoe and seeds. This corn yield of
Table 1.1 ENERGY INPUTS IN CORN PRODUCTION IN MEXICO USING ONLY
MANPOWER (PIMENTEL AND PIMENTEL, 1979)
Inputs Quantity/ha kJ/ha kcal/ha
Labor 1144 h 2462690 589160
Ax + hoe 69260 kJ 69260 16570
Seeds 10.4 kg 153020 36608
Total 2684970 642338
Corn 11994444 kkgg 28847020 6901200
kJ output/kJ input 10.74
1944 kg/ha provided about 28.8 miUion kilojoules (kJ) (6.9 million kcal) of
food.
Gradually humans have augmented their own power with other sources
of energy, first animals, then wood and coal. But it wasn't until the
twentieth century that fossil fuel became the dominant fuel, especially in
the industrialized nations. Now, in these countries, fossil energy powers
crop and livestock production and is as vital an agricultural resource as
land and water.
6 World outlook for food
Of course, manpower is still used, but it is a relatively small input. Under
present mechanized systems, only about 8 h of on-farm labor are required
to produce 1 ha of corn compared with producing corn by hand, which
requires about 1200 h of labor. This is more than a 100-fold difference
{Tables LI and i.2).
Although fossil energy is expended in many phases of food production,
the major uses of energy in actual crop production are for the fuel to run
farm machinery and for the manufacture of fertilizers and pesticides {Table
1.2). Both pesticides and nitrogen fertilizers are produced directly from
fossil energy. Pesticides are made primarily from petroleum, while nit
rogen fertilizer is made from natural gas.
Table 1.2 ENERGY INPUTS PER HECTARE FOR CORN
PRODUCTION IN THE USA (PIMENTEL AND BURGESS, 1980)
Quantity/ha kJ X Κ
Inputs
Labor 8.05 h
Machinery 55 kg 4.14
Gasoline 26.96 € 1.14
Diesel 78.45 € 3.74
Liquefied petroleum gas 34.54 € 1.11
Electricity 3L62 kWh 0.38
Nitrogen 135 kg 8.30
Phosphorus 65.04 kg 0.82
Potassium 95.32 kg 0.64
Lime 354.35 kg 0.47
Seeds 23.79 kg 2.49
Insecticides 2.47 kg 0.90
Herbicides 5.14 kg 2.15
Transportation 186.04 kg 0.20
Total 26.48
Output
Total yield 8000 kg 117.04
kJ output/kJ input 4.42
Yearly about 1500 £ of oil are expended to produce, process, distribute
and prepare the food for each American. Collectively this represents about
17% of the total energy used in the USA each year (Pimentel and
Pimentel, 1979). Agricultural production uses only about 6% of total
energy, while food processing, packaging, transport, storage and home
preparation together use the remaining 11%.
For example, to raise 1 ha of corn, a typical grain crop, in the USA,
approximately 600 € of gasoline equivalents are required and this is
equivalent to an expenditure of about 1 € of gasoline per 9 kg of corn
produced. Or put another way, about 4 kJ of corn are produced for each kJ
of fossil energy expended {Table 1.2). For corn, approximately one-third
of the fossil energy is used to make fertihzers and another one-third is used
to power the various farm machines. For most grain production in the USA
only 0.25 to 0.5 kJ of fossil energy are expended per kJ of food produced.
David Pimentel and Marcia Pimentel 7
Producing other food crops, however, is not as energy efficient as grain
production. For example, in apple and orange production, 2-3 kJ of fossil
energy are expended per kJ of food produced (Pimentel, 1980) and in
culturing vegetables 1-5 kJ of energy are expended per food kJ produced.
Although fruits and vegetables require larger energy inputs per food kJ
than grain, neither are as energy-expensive as producing animal protein.
From 10 to 90 kJ of fossil energy are expended to produce 1 kJ of animal
protein (Pimentel et ai, 1980). Animal protein products are significantly
more energy-expensive than plant protein because forage and grains have
first to be grown, then consumed by animals, who in turn are used as
human food. The forage and feed that maintain the breeding herd are
additional energy costs. At present in the USA about 90% of the grain
produced is cycled through livestock to produce the milk, eggs and meat
that consumers prefer (Pimentel et aL, 1980).
Yet many of these grains are entirely suitable for human food. Thus an
important consideration for future planning would be to use the grains
directly as food and thereby decrease energy expenditure.
Fertilizer is responsible for costly energy inputs in modern agriculture
and therefore ways to reduce this energy expenditure, while adding
necessary nutrients to farm lands, need to be developed. One way that
TOTAL ENERGY USE
Food
sy Stenn
Industrial
Connnnercial
Transport
Residential
ENERGY USE IN FOOD SYSTEM
Processing
and
packaging
Agriculture
Distribution
and
preparation
Figure 1.2 Percentage of total energy used in the US economy and the proportion expended
specifically for agricultural production, processing and packaging, and distribution and
preparation
