The one epiphany that awed him was the concept of stacking functions. This is a basic concept in permaculture design where elements serve more than one function. Being a young person, this seemed like something really new to him. With me, being old, it wasn't all that astounding. It's like killing two birds with one stone, a saying that has existed long before I was born.
Examples of stacking functions on my own homestead (although I'm not a permaculture farm, though I use ideas from all sorts of farming methods.....
... Cholesterol spinach grows in my Secret Garden. From time to time it gets straggly, so I prune it, giving it a new lease on life. The young leaves and tips I save and set aside for eating. The slightly older leaves and stems go into the livestock cook pot. The woodier stems go to the nursery for potting, thus creating new plants to expand the gardens. So my labor has stacking functions -- I am cleaning up the garden, improving the vitality of a crop, harvesting food for us, harvesting feed for the animals, and propagating a crop.
... Plants can have multiple functions, such as my food forest trees. Some of my vining crops have homemade trellises, but others climb trees. Those trees are food bearing themselves, plus they serve as trellises for the vine crop. So the trees provide food, shade for a second crop to grow, and support for the vines. Of course trees also increase humidity, capture CO2, improve soil, provide mulch or compost material (fallen leaves), and eventually wood for firewood, wood crafts, and hugelkultur pits.
... My chicken operation is set up as stacking functions -- the provide meat, eggs, and manure. They churn up compost (which I add to their pen), enriching it in the process, and removing any insects/slugs/mice. They process grass clippings that I give them into a nutrient garden resource. Their food is primarily garden waste recycled through them to become manure, and ultimately garden fertilizer. So they help rid the farm of excess waste and convert it to a valuable product. Plus their pen has a tarp roof from which I can collect rainwater. On top of that serious stuff, I find them to be a source of amusement....cheap entertainment.
Most things on a homestead style farm have multiple functions.
... A perimeter fence keeps livestock and pets in, but just as importantly keeps other animals and people out. The fence may also provide trellis support for crops such as peas or beans. Some fences can function as windbreaks or visual screens blocking out unwanted views.
... A pond provides a pleasing venue for picnics in addition to mosquito control, a place to raise fish or grow aquaponic lettuce, a source of compost or livestock feed materials (via pond plants), a source of water for irrigation or fire fighting, a beneficial wildlife setting.
Stacking functions Is so normal for me that I don't even give it much thought. Everything on this farm seems to have more than one purpose. But to be truly stacking functions in the permaculture sense, it has to be in the design. Stacking functions afterall is a design principle.
Some stacking functions I knowingly incorporated.....
...sheep. They mow the grasses and weeds, provide manure, provide lambs for sale, give us meat and milk.
...our little barn. It was built with the ideas in mind to be a secure storage building for equipment, house a workshop, give me a place to work on rainy days, an emergency shelter for bummer lambs, collect rainwater for the ag catchment tank, and serve as a sleeping spot for unexpected overnight guests.
The thing I see about the permaculture principle of stacking functions is that it increases efficiency. One gets more done during a time period. Or gets more return out of a space or project. Or in the example of the sheep, eliminates the need for added elements, such as a lawnmower or the time needed for mowing or weedwacking. In permaculture, stacking functions is part of the design that goes into creating the system. It's not an after thought or a lucky bonus. As I was learning while creating my homestead, I naturally started incorporating multiple purposes. Without being aware of it, I was creating my own idea of stacking functions. I've gotten so bad that I can't bring myself to take a trip to town without stopping at the dump, checking out the dump thrift store for new goodies, picking up a gallon or two of fresh drinking water, doing my in-town errand, swinging by the post office to check for mail, perhaps stopping for a cup of coffee and a bit of conversation. doing a tad of foraging in the right season, and stopping someplace to enjoy the view before heading home.