Renewable and Sustainable Energy Reviews 13 (2009) 11331137

Contents lists available at ScienceDirect

Renewable and Sustainable Energy Reviews

journal homepage: www.elsevier.com/locate/rser

Sustainability: An integral engineering design approach

Tony Pereira
Department of Mechanical and Aerospace Engineering, University of California Los Angeles, 420 Westwood Plaza, ENG IV 48-121, Los Angeles, CA 90095, United States

A R T I C L E I N F O

A B S T R A C T

Article history:
Received 30 April 2008
Accepted 2 May 2008

The work described in this paper won an Engineering Award from the UNESCO and the United Nations. It
qualied among the top 30 nalists from a pool of about 3200 engineering entries from the worlds most
prestigious universities in 89 countries, including Cambridge, Oxford, MIT, Stanford and Yale. This paper
describes the methods employed in a sustainability project titled Global Basic Needs in an Integrated
Sustainable Approach submitted by the author to the UNESCO in agreement with the United Nations
Millennium Goals and within their framework of the Mondialogo Engineering Award. A six-nation
international jury of renowned leading scientists and engineers selected this project for a nomination
award. While we all anxiously wait for science to provide the solutions to global warming and
catastrophic climate change, a holistic engineering approach was used to halt pollution, and to provide
sustainable shelter, clean water, energy, food and education to the global population. This approach can
be used anywhere in the world and conceptualizes a revolutionary sustainability paradigm for present
and future societies. This work is a contribution to the advancement of the science of sustainability
everywhere on the planet.
2008 Elsevier Ltd. All rights reserved.

Keywords:
Sustainability
Appropriate engineering
Solar energy
Organic
Renewable
Mondialogo

Contents
1.
2.
3.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Integral design method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction
Sustainability is solely an inherent property of natural
ecosystems, in which there is mass and energy balance [1]. It is
misleading to believe that a resource such as a crop is sustainable
only because it is renewable. Many crops used for human
consumption are renewable only with a large input of resources
[2]. Hence, it can be safely stated that human sustainability is
possible only when it follows natural laws of mass and energy
balance, and is, therefore, an extremely complex issue. The reasons
for this complexity are clearly owing to its direct connections to
the natural systems of the planet air, water, soil and sunlight
that sustain and make all life possible. These elements are
intrinsically and inextricably interconnected in an entropic cycle
of
life
E-mail address: apereira@ucla.edu.
aURL: http://www.ise.seas.ucla.edu.
1364-0321/$ see front matter 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.rser.2008.05.003

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nd death, and in a permanent state of ux. Extensive scientic

studies on the human consumption of global resources have been
done in recent decades that clearly conrm that the human species
is on a brutal collision course with its natural environment [36].
Two fundamental studies that quantify the extent of human unsustainability are mentioned here. The rst is Vitousek et al.s
seminal work on the human appropriation of the products of
photosynthesis done at Stanford University [7], and the second, the
revolutionary human footprint calculations by Rees and Wackernagel at the University of British Columbia [8]. These two studies
led the work to the rigorous scientic calculation of the human
species impact on its environment. In spite of scientic advances,
global consumption continues at ever increasing rates to this day,
and not much progress has been achieved to halt and reverse the
effects of the unsustainable use of resources by the ever increasing
human population [9]. The consumption driven modern way-oflife continues un-abated in all fronts, everywhere. Therefore, other
approaches need to be explored. A holistic approach that uses an

T. Pereira / Renewable and Sustainable Energy Reviews 13 (2009) 11331137

1134

integral engineering method to provide for the primary needs of

the population shelter, water, food, energy and education is
detailed in this work. This method takes into full account the
conservation of mass and energy of the natural ecosystems.
The project main intent was to offer a solution to the overall
improvement of the living conditions of the over 3 billion of the
worlds population mostly in undeveloped countries who have no
access to clean water or food [10,11]. About 3.7 billion people, i.e.,
more that half of the current world population are malnourished,
according to data published by the World Health Organization. The
design approach consists of eight major components integrated
into a fully-functional system designed to work in harmonious
symbiosis with the living environment: passive solar shelter with
rainwater catchment system, pre-ltering and cistern, solar energy
for lighting, hot water and cooking, compost toilets with urine
separation, mini-marsh greywater system, and an organic garden
and compost bin.
2. Integral design method
The general approach to sustainability is generally deeply
awed. Its main answer consists typically at throwing a perceived
green solution e.g., wind, hydrogen, biomass, nuclear or solar
energy to real world problems water, waste, food or energy in
one single plug-in format to existing systems, while leaving all
other existing issues associated with the un-sustainable existing
structures untouched and in place. The underlying causes of the
existing environmental, health and socio-economic problems are
left intact for most cases, therefore the insignicant amount of
progress that has been achieved after decades of struggle towards a
sustainable society. Sustainability solutions addressing the needs
of society and its use of resources must take on a whole systems
analysis, and subsequently, a whole systems implementation.
Nature and human interactions with the natural environment
cannot and should not be seen as isolated from each other.
To obtain a clear perspective, it is best to enter sustainability from
the back door, i.e., to rst take a glance at what is not sustainable.
With less than 5% of the worlds population, the United States
consumes about 1/3 of the worlds resources, many of which are
already overexploited [911]. Elementary algebra says that three
countries with the same size of the U.S. and consuming at the same
rate as the U.S. does, would consume 100% of everything. That would
also mean that less than 15% about 1/7 of the worlds population
would consume all of the worlds resources at those rates (see Figs. 1
and 2). Europe, with a population comparable to that of the U.S.,
now consumes just about as much as the U.S. does, and gobbles

Fig. 1. U.S. population versus world consumption.

Fig. 2. Consumption at U.S. levels.

another 1/3 slice. That leaves about 1/3 of the worlds resources to be
shared by well over 3/4 (85%) of the worlds population. One more
country the size of the U.S. consuming at the present U.S.
consumption levels which is not terribly difcult to imagine
and there will be nothing left to share. Elementary algebra again tells
us that at current rates of extraction and consumption by developed
countries, not one, two, three, four, ve, or six, but just about seven
planets with the same abundant resources air, water, sunlight,
trees, animals, plants, oil and soil would be needed to sustain the
current world population at industrialized living standards. In the
end, we would leave those seven planets ozone depleted, warmed
up, species extinct and inhabitable no doubt like we are doing to this
one. Furthermore, with only about half of a percent of the worlds
total biomass, the human species manifests itself as an incredibly
demanding species on its environment by gobbling up 50% of the
global products of photosynthesis [7], see Fig. 3. Clearly, the planet
has too many people for the available resources of land, water, and
energy [46]. The current world population is about 6.7 billion and
growing at 100 million each year. The demands of the current
population are at a real-time 120% over and in excess of what the biocapacity and regenerative systems of the planet can work out and
therefore we are already depleting the natural stores of the planet at
that ratio every second [8]. As seen above, at current levels of unsustainable and nonsensical consumption, splurge and waste, the
Earth carrying capacity is about one billion people. Less than 2 billion

Fig. 3. With about half of 1% of the total biomass on the planet, the human species
appropriates about half of the total products of photosynthesis. Clearly, doubling
the current world population would entail one hundred percent appropriation of all
the products of photosynthesis solely by the human race at current consumption
levels.

T. Pereira / Renewable and Sustainable Energy Reviews 13 (2009) 11331137

Fig. 4. Energy ow. Most world energy us is derived vast stores of buried sunshine,
i.e., coal, oil and natural gas. Once exhausted, energy used must revert to a steadystate use of sun energy.

is estimated for a sustainable human society where conservation

and non-polluting lifestyles are adopted everywhere [46]. These
simple, yet effective calculations should be sufcient to clearly put
into perspective the brutal side of the human species current path of
un-sustainability [711,46].
From the current total 15 TW of energy from all sources
consumed by humans, the largest percentage is obtained directly
from stored sunshine, i.e., the energy contained in deposits of coal,
oil and natural gas [911]. It took more than 700 million years for
oil, natural gas, and coal to accumulate in a random geological
boon process that is also extremely unlikely to happen again any
time soon [2]. Once the Earth stored energy deposits are exhausted,
with no indications at the moment that they will not be in addition
to all the consequences that are becoming increasingly more
evident such as global warming, the only other available option is
to revert to a steady-state of energy consumption that relies on the
energy directly obtained from the sun (see Fig. 4). In 1 h, the Earth
receives as much energy from the sun as the global human energy
consumption in one entire year from all sources. Therefore, a
decentralized, local-economy based, self-sufcient and happy
global human society is entirely possible. The economics of
sustainable societies only recently have started to come to light in
the works of prominent authors who dared to challenge the absurd
theories of classic economics and its disastrous consequences
[47,48]. The purpose of this work is to undertake the transition to a
solar powered steady-state model immediately and without delay.
Addressing the basic needs common to all human beings
shelter, water, food and education from an integral systems
perspective where there is conservation of mass and energy is
essentially the key to achieve mass and energy balance (see Fig. 5).
Sunlight is converted into electrical energy to provide lighting
required for reading and education. Sunlight is also used directly
for solar cooking eliminating both the need to gather rewood and
the pulmonary problems associated with smoke from re inside
the house. A solar cooker was designed directly into one of the sun
facing house walls offering the convenience of a permanent

Fig. 5. Basic global human needs are shelter, water, food and education. They are
required to support all human activity, which in turn must be supported by soil,
water and sunlight on which we all depend.

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appliance. Sunlight is also used to heat water for cleaning and

washing. All the rainwater is collected by a catchment system and
stored in a cistern for drinking and washing, and for garden use
when it is sufciently abundant. Water used in washing and
cleaning is gravity fed to a mini greywater marsh and used directly
in the organic garden afterwards. No chlorine, detergents, hard
soaps or chemicals are allowed in this process. Human waste is
composted in a compost toilet that eliminates the use of water and
its associated sewer system. Solid wastes from food preparation
and cooking are composted in a compost bin. The compost hence
obtained is used directly in the organic garden to build the soil,
create humus, soil fertility, provide fresh produce, fruits and
vegetables and maintaining and replenishing the water table.
Notice the circular arrow ow between solar cooking, solar hot
water, greywater marsh, compost toilets, compost bin and organic
garden going back to solar cooking which re-establishes the
natural nutrient cycle required to sustain life (see Fig. 6). The eight
main design elements are integrated into a whole functioning
sustainable system, as follows:
I.
II.
III.
IV.
V.
VI.
VII.
VIII.

Passive Solar House

Rainwater Catchment System, Pre-ltering & Cistern
Solar Energy & Lighting System
Solar Domestic Hot Water System
Solar Cooking w/Backup High-Efciency Wood Stove
Compost Toilets w/Separate Urine Collection
Mini-Marsh Greywater System
Organic Garden & Compost Bin

I. Passive Solar House: The main structure is built using ageless,

natural and non-toxic materials that can be obtained locally
and with thermal properties suitable for both cold and hot
weather climates such as reinforced adobe, pressed earth
block, or strawbale [1215]. Local availability, material
familiarity, economy and very low energy required for its
production are the key factors for this selection. These
building materials store solar heat during the day and release
it slowly to the interior throughout the night during cold
periods, thus providing temperature stabilization for the
interior and thus avoiding the use of energy dependent
heating or cooling by mechanical air conditioning systems.
The structure is oriented in the EastWest direction alongside
its larger dimension following passive solar design guidelines,
with dimensionally designed awnings, trellises and windows
to take full advantage of latitude, insolation and prevailing
winds [1620].

Fig. 6. The use of sun energy, water, food and wastes for sustained human activity.
The circulation of water and solid waste to the organic garden and back to solar
cooking in the form of food re-establishes the vital nutrient cycle (blue arrows). (For
interpretation of the references to color in this gure legend, the reader is referred
to the web version of the article.)

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T. Pereira / Renewable and Sustainable Energy Reviews 13 (2009) 11331137

II. Rainwater Catchment System, Pre-ltering and Cistern: All the

rainwater from the roof is collected. The rainwater is cleaned
and pre-ltered from debris, and is stored in a cistern where it
can be used primarily for drinking. Washing and irrigation
uses are also acceptable when there is excess water from
abundant rain [2123]. About 25 l/m2 of roof can be
effectively collected for each cm of precipitation from rain.
With a relatively small roof surface of about 100 m2 and as
little as 25 cm of precipitation annually common to many
areas normally considered as being deserts, about 62,500 l of
rainwater can be collected per year, by no means a small
amount. While only a relatively small portion of the Earth
enjoys plentiful rain precipitation, the water conservation and
re-use methods employed throughout by the integral
engineering design approach drastically reduce the amounts
normally prescribed per capita, hence making the amount of
collected water above very signicant and suitable for many
other uses in addition to drinking.
III. Solar Energy & Lighting System: Solar energy is captured from
the roof with a set of photovoltaic panels (300 W total).
Energy will be stored in a deep-charge battery to be used for
interior lighting with compact uorescents (513 W) and
LEDs (15 W). The solar energy system will provide about
1500 Wh/day in most climates, sufcient for most lighting
needs required for educational purposes [2426].
IV. Solar Domestic Hot Water System: Also on the north side of the
house, a simple domestic batch solar hot water tank will be
built to warm water for a low-ow solar shower and hand
washing. No detergents, bleach, phosphates, commercial
soaps or cleaners will be allowed in the system, only simple
natural soaps that can be either fabricated or purchased
locally [27].
V. Solar Cooking w/Backup High-Efciency Wood Stove: On the
north side of the house, a solar cooking oven will be built with
access from the inside of the house for preparing and cooking
hot meals [28]. This will mostly eliminate the use of rewood
and the time required to gather it, and the devastation to wild
forests that comes with this practice [10,11]. For cloudy days
when the sun does not shine, a backup wood stove of a snug
design and high-efciency combustion chamber will be
constructed inside the house [29,30].

VI. Compost Toilets w/Separate Urine Collection: A composting

toilet with separate urine extraction will be built in the home.
Composting toilets do not use or pollute water, thus conserving
a huge amount of the precious life-giving liquid vital for other
uses. Human waste and urine are a vital resource [3134]. Urine
collection diluted with greywater will be used in the garden to
provide additional irrigation and fertilizer (333 NPK). When
properly composted to a ratio of about 30 parts of carbon (about
one coffee size can of shredded leaves, sawdust, etc. added to
the compost toilet after each use) to one part of nitrogen present
in human waste, the temperature in the compost toilet pile will
raise to about 5575 8C and will kill all the pathogens present in
human waste [32]. The humus produced in this process can
safely be used in the organic garden outside to build-up and
enrich top-soil, re-establish the nutrient cycle, improve soil
fertility, eliminate the need for municipal sewer systems and its
associated problems of pollution of rivers, waterways, rivers
and streams, and to grow fresh food, fruits and vegetables
required for healthy nutrition and dietary needs of the
population. This arrangement is both suitable to rural and city
areas as demonstrated by the recent opening of the 2800 m2
C.K. Choi ofce building at the University of British Columbia,
Vancouver, Canada that is not connected to the municipal sewer
system.
VII. Mini-Marsh Greywater System: Water used in washing is
directed to a mini greywater marsh system where it is preltered from grease and solid debris. The roots of cattails and
bulrushes lter the remaining nutrients in suspension and
build plant life with very low or no vector problems. The
cleaned water is used for irrigation in the organic garden. Only
a handful of plant species adapted to the region are required in
this mini-marsh, mostly from the cattail family or equivalent
[35,36].
VIII. Organic Garden & Compost Bin: The organic garden is built
using organic and bio-intensive methods. Heavy soil mulching
can cut the amount of water usage up to 75% when compared
to wasteful conventional irrigation methods. Using closely
spaced, multicroping, and green crops creates and maintains
soil fertility and completely eliminates the use of fossil fuel
dependent chemicals, fertilizers, pesticides and herbicides
[3739]. The organic garden is designed with swales on

Fig. 7. The integral sustainable engineering design approach. North orientation in the south hemisphere, and vice-versa. All elements work in symbiosis and harmony to clean
the water and air, re-establish the nutrient cycle by processing human waste, and support life.

T. Pereira / Renewable and Sustainable Energy Reviews 13 (2009) 11331137

contour along the natural slopes of the plot terrain to catch all
the ground running water from rains, and heavily mulched to
prevent water evaporation and allow the slow permeation of
water into the local water table [40]. A compost bin is built to
compost the garden wastes from crop rotations and other
vegetable wastes coming from the house and the kitchen such
as fruit skins, waste paper and vegetable peels. The organic
compost obtained from the composting toilets in addition to
the compost obtained from a compost bin will be used in
the organic garden [32,37]. Expected yields of fruits and
vegetables using bio-intensive cultivation methods are about
15 kg/m2 per year, or about 60 metric tons per acre per year,
well above what is obtained from chemical conventional
methods [37,38]. Additionally, a 75% reduction in irrigation
water use is also expected due to the higher moisture
retention of mulched organic soil, and the additional benet
that there will be no land, people, water, air or animal
exposure to the risks of toxic pesticide use and contamination,
and its associated pollution of waterways [41]. Considering
that the average meal travels about 1500, 5000 and 6800
miles to arrive at the American, Canadian and Japanese tables,
respectively, and that it takes about 10 calories to produce one
calorie of the food we eat today, the reverse of what was
required just a short 50 years ago [4145], the soil is the place
where it all comes together air, water, sunlight into the
magic of life, and the most signicant aspect of the project (see
Fig. 7). Only the most profound humbleness can truly
appreciate the unfathomable and awesome symbiosis that
coalesces in all that is alive and aware in the natural world.

3. Conclusions
The recognition given to this project by the world community
and the distinguished international jury signies a very welcome
worldwide shift in awareness and critical thinking towards
sustainability. The change to a sustainable way of life is required
everywhere without delay if our species is anything but serious
about its own future in this far corner of the universe. We looked at
the system design from an integral point of view, not just as a
combination of isolated plug-in components. From a systems
perspective, the cycle is closed. Food, water, air and sunlight are
used in a continuous entropic cycle that works in support of human
activities, and vice-versa. There is no waste, and additional inputs
of energy or resources should not be required. A sustainable
system designed in this fashion is therefore autonomous, selfsufcient, self-regenerating, completely independent of distant
resources and fossil fuels, and in stark contrast with current
uncontrolled consumerism.
A signicant purpose of this project is to serve as a multidisciplinary research platform to obtain rigorous scientic data
validating the integrated sustainability approach for publication in
worldwide access peer-reviewed journals, to model sustainability,
to spread appropriate engineering knowledge to effectively
combat and stem man-made climate change and global warming,
achieve global security, education and energy independence, and
to establish and develop the science of integral sustainable systems
engineering, design and development.
Acknowledgements
The author wishes to thank and express his appreciation to the
UNESCO, the Educational, Scientic and Cultural arm of the United

1137

Nations and Daimler for their visionary work and for making
possible the inter-cultural exchange and dialogue of science and
sustainability worldwide by means of the international Mondialogo Engineering Award competition, and to Prof. David
Pimentel, College of Agriculture and Life Sciences at Cornell
University for reviewing the manuscript and his many comments
and suggestions.
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