Permaculture Designers Manual
CHAPTER 2 – CONCEPTS AND THEMES IN DESIGN
Section 2.5 –
Yields can be thought of in immediate, palpable, and material ways, and are fairly easily measured as:

Permaculture Designers Manual
CHAPTER 2 – CONCEPTS AND THEMES IN DESIGN
Section 2.5 –
Yields can be thought of in immediate, palpable, and material ways, and are fairly easily measured as:
I. PRODUCT YIELD
The sum of primary and derived products available from, or surplus to, the system. Some of these are Intrinsic (or precede design), others are created by design.
II. ENERGY YIELD
The sum of conserved, stored, and generated energy surplus to the system, again both intrinsic and those created by design.
Impalpable yields are those related to health and nutrition, security, and a satisfactory social context and lifestyle.
Not surprisingly, it is the search for these invisible yields that most often drives people to seek good design or to take up life on the land, for “what does it benefit a man if he gains the whole world and loses his soul?”
Thus, we see the invisible yields in terms of values and ethics. This governs our concept of needs and sets the limits of “enough“. Here, we see an ethical basis as a vital component of yield.
Although all systems have a natural or base yield depending on their productivity, our concern in Permacuiture Is that this essential base yield is “sustainable“.
Several factors now operate to use the yield of natural systems. In the simplest form, this is the overuse of energy in degenerative systems due to the unwise application of fossil fuel energy.
“The energy provided by natural gas and crude oil have had an incredible impact on the productivity of the agricultural sector – with some expert studies indicating Western agricultural practices utilize 10 calories of petroleum energy to produce one calorie of food (other global agricultural regions are not so energy intense). Prior to the Age of Oil the energy input was much closer to the energy output of the food produced. Experts claim that without hydrocarbons the agricultural sector could only feed 3 billion people – less than one-half the current global population of 7 billion.“
“Poisoning by unproductive use” is observable and widespread.
Thus we must concentrate on productive use, which implies that the energy used is turned into biological growth and held as basic living material in the global ecosystem.
Unused, wasted, or frivolously used resources are energies running wild, which creates chaos, destroys basic resources, and eventually abolishes all yield or surplus.
In design terms, we can find yields fnom those living populations or sorces which are the stocks of the biologist (the so-called standing crop) or from non-living systems such as the climatic elements, chemical energy, and machine technology.
There is energy stored by extinct life as coal, oil, and gas; energy left over from the formation of the earth as geothermal energy; tides; and electromagnetic and gravitational forces. Cosmic and solar energies impinge on the earth, and life intercepts these flows to make them available for life forms.
In our small part of the system (the design site) our work is to “store, direct, conserve, and convert to useful forms these those energies that exist on, or pass through, the site.”
The total sum of our strategy, in terms of surplus energy usefully stored, is the “system yield of design“.
Definition of System Yeild
“System yield is the sum total of surplus energy produced by, stored, conserved, reused, or converted by the design.”
Energy is in surplus once the system itself has available all its needs for growth, reproduction, and maintenance.
Some biologists may define yield or production in more narrow terms, accepting that a forest, lake, or crop has a finite upper limit of surplus due to substrate conditions and available energy.
We do not have to accept this, as it is a passive approach, inapplicable to active and conscious design or active management using, for example, fertilizers, windbreaks, or selected species.
Even more narrowly defined is the yield of agricultural economists, who regard a single product (peaches / ha) as the yield. It may be this approach itself which is the true limit to yield!
A true accounting of yield takes into considuation both upstream costs (energy) and downstream costs (health). The “product yield” may create problems of pollution and soil mineral loss, and cost more than it can replace.
The very concept of surplus yield supposes either flow through or growth within our system. Coal and rock do not have yield in this sense; they have a finite or limited product. Only life and now can yield continually, or as long as they persist.
Thus the energy stocks of any system are the flows and lives within it. The flow may exist without life (as on the moon), where only technology can intervene to obtain a y