We’re adding an addition to our home. Yup, we’re taking on another home improvement project. After the mudroom, I had my reservations about another project, but weighing the pros and cons, we decided the benefits outweighed the discomfort and costs of a construction project. Firstly, we would have room to add a dining table and invite guests over for Thanksgiving, Passover or just a regular dinner around a table. Secondly, we would be able to have office space, which with Eric’s new job, is becoming increasingly necessary. Thirdly, we could add a greenhouse that would allow us year-round production of produce.
Eric spent a weekend in April at the Canelo Project with the Steen’s who wrote the book on strawbale homes. We know we want to continue with strawbale building as we love the amazing thermal mass, as well as ease of construction. However, we still weren’t sure about how to build the greenhouse. We want to extend our grey water system from our garden and divert it back into the greenhouse. We create plenty of grey water and always have an abundant amount year-round. We decided to use our friendly neighborhood biotecture genius for inspiration.
Earthships
We live down the road from the Greater World Earthship Community and Earthship Visitor Center founded by Mike Reynolds. Earthships are homes built of recycled materials (such as tires, aluminum cans, and bottles) to be entirely self-sustaining. They catch their own water like we do and funnel it through a complex system of grey water and black water filters, reusing the water in a multitude of ways, including to grow food indoors and out. Unlike us, they use flush toilets, but have a system of filtering black water so it is not toxic. They use solar power electricity and are heated solely by passive solar and thermal mass. They were created after years and years of experimentation that continue to this day to create the most optimal models. Earthships are built all over the world, including in underdeveloped countries where they have plenty of trash for building materials and not much money. They aren’t entirely inexpensive to reproduce we learned as the off-grid systems they use are much more elaborate than our simple DIY set-up.
What do you think? Have you ever visited Earthships? Would you like to live in an Earthship?
We decided to get a guided tour of the Earthships to see if we could get some inspiration on how to create our new indoor greenhouse. We lucked out with our highly informed guide, Will Ore, and a very small group of people on tour so we could ask lots of our own questions. (One person on our tour was filming for PBS News Hour, so you might see us on TV.)
This is what we learned for our greenhouse grey water system.
For their system, they have a shower on one end of the greenhouse and a toilet on the other. The grey water from the shower goes through the garden beds called botanical cells, being filtered along the way, and is pumped back up to be reused in the toilet. (Note: their kitchen sink water goes straight to the black water or septic because of excess grease.)
Botanical cells are lined with rubber. You can plumb anything into the botanical cells. One end is 4 1/2 feet deep, and the other end is 5 1/2 feet deep.
The shower gravity feeds water initially into the reception cell within the larger botanical cell. The reception cell is a wooden box lined with metal flashing to protect the wood and with holes drilled into it, sitting on a rock bowl. The water travels through the reception cell into the rocks and then into the rest of the botanical cell where there are a couple feet of gravel on the bottom, topped with a layer of sand and the rest is soil. Commonly grown in Earthships are figs, rosemary, lime trees and banana trees. Companion planting and sacrificial plantings are often utilized.
At the far deep end of the botanical cell there are two PVC pipes sitting in rock bowls with drilled out holes at the very bottom. There are DC powered submersible pumps at the bottom of the PVC pipes that you could find in any pool supply store. The recirculation pump goes back to the beginning of the cell to start the process all over again and is on its own solar panel that runs all day. The other pump goes to the toilet, connected to a pressure switch sensing toilet bowl pressure with a charcoal filter to make sure the toilet water isn’t yellow. (I guess some people care about this.) Sometimes there is a peat moss filter in the cell too as a last stage of filtration before the pumps.
Once flushed, the toilet black water goes to a buried septic tank and the overflow goes into outdoor trenches built similarly to the indoor botanical cells where trees may be planted. Finally, the water enters a leach field for whatever is left to evaporate or sink into the soil.
So, the water is used 4 times after it is caught off the roof and filtered. The first use is washing and drinking, the second use is for watering the greenhouse, the third use is for the toilet and the fourth use is for outdoor landscaping. What an amazing way to fully utilize your water, especially in the desert!
I asked about concerns regarding toxins or microplastics going into food in the garden beds. Will said that they don’t worry about that as the plants are able to filter it themselves.
Comparing this to our system
We use a compost toilet, all of our water including the kitchen sink goes into our outdoor garden (and soon a greenhouse too), and we use a much simpler water filtration system, drinking from our tap water without reservation. Our thermal mass is strawbales instead of tires. (I have often wondered if off gassing from the tires is a possibility.) Like Earthships, we use solar power and with the greenhouse we will add even more passive solar energy. This part will be a bit of an experiment to see if we will need an interior glass wall to separate the greenhouse or if it will be sufficient to have it in our living space. Since glass isn’t cheap, we’ll start without the interior wall and give it a winter to see how it feels.
After visiting the Earthship, we have decided to build a version of the botanical cell. We probably don’t need a reception cell since our grey water is already going through buckets of gravel on its way to our garden.
We’ll keep you updated on our addition as we go. For now, just lots of digging, so much digging.