Aquaponics

Published in the Sun October 30, 2011

Sometime around 1880, a Walburg farmer hand-dug a cistern to collect rainwater off his roof.  The cistern is big, about eight feet across and thirty feet deep, and completely lined with large stones.  It was built to last, and it has, for 130 years, but it is no longer used to collect rainwater.  If that farmer were to visit today he would be astonished to see what Bob and Janine Hall are doing with his cistern.

It starts with the Halls washing machine.  With several kids at home they run about twelve loads of laundry a week.  The graywater from the washing machine runs directly into the cistern.  There is a five foot opening covered with wire mesh at the top of the cistern, so you can easily look down and see the water, which looks very clean.  (Janine uses Seventh Generation laundry detergent, which is phosphate free.)  From the cistern the water is pumped into three 330 gallon tanks.  The tanks provide water for two raised gardening beds about the size and shape of pool tables.  But there is no soil in these beds; they are filled with river rock and crushed granite.  The first bed is crowded with lush, dark green tomato plants.  The other bed is newly planted with strawberries.

Both beds are equipped with an ingenious drain that allows them to automatically fill with water and then drain completely every two hours.  The surface of the gravel stays dry in the sunshine so that algae will not grow.  The tomato bed drains into a plastic pond stocked with forty small goldfish and some aquatic plants.  The pond water, which contains waste from the goldfish (and goldfish are prolific with waste) drains back into the cistern.

The ammonia waste from the fish provides nitrogen and other nutrients for the plants.  The plants, by consuming the nutrients as fertilizer, clean the water for the fish.  This symbiotic relationship between gardening and fish is called aquaponics.  The word aquaponics is a combination of the words “aquaculture”, which means fish-farming, and “hydroponics”, which means raising vegetables in nutrient-rich water.  As long as the fish and the plants are in balance, the water can be recycled through the process indefinitely.  Contrary to what you might think, aquaponics uses only 10% of the water that a dirt garden would consume.  Bob has used only washing machine water to keep his cistern filled all summer.  In fact, not only does the cistern provide water for the aquaponics system, but also for six baby fruit trees, three dogs, five goats, four sheep, three horses, and a flock of chickens.

Actually, the system just described was only Bob’s starter project.  Now he has built a large greenhouse holding five larger planting beds flourishing with peppers, lettuce, and broccoli.  There is also a hydroponic “raft” in which plants are suspended in the water without the stones.  Bob lifts up a lettuce to demonstrate the bare roots extending 12 inches into the water.  We follow the PVC pipe to a separate room at the end of the greenhouse housing a 550 gallon tank of tilapia.  The tilapia are more sensitive than goldfish, but can be harvested and eaten when they get big enough.  The tilapia reproduce in the tank.  The mother carries the eggs in her mouth until they hatch, and even after hatching she will protect hundreds of babies in her mouth until they can manage on their own.  A good aquaponics farmer can end up with a continuous supply of delicious and mercury-free fish for supper.

At one point the Halls had the tilapia outside in the goldfish pond, but unfortunately there were tragic consequences.  One night Janine noticed some movement around the pond.  Going closer with a light, she noticed a 5 foot water moccasin slithering out of the pond after a tasty snack.  Shining her light down into the cistern she saw more huge moccasins.  I wish I could have seen with my own eyes what happened next.  Bob fetched his shotgun and started blasting away into the cistern.  After the massacre they fished eight dead snakes out of the water.  But it was too late; most of their tilapia were gone.

Eventually Bob and Janine plan to sell produce from their aquaponic greenhouses, as well as provide themselves with all the fresh vegetables they can eat.  Bob says he can get 8-10 times the produce in half the time out of his aquaponic beds that he could get from his old dirt garden.  He can farm year round, and with aquaponics he doesn’t need pesticides or chemical fertilizers.  Plus there are no weeds to pull.

The Hall’s former dirt garden lies drought parched and abandoned beside the barn.  A chicken, searching for a bug she might have missed, scratches in the dust.

Graywater

Published in the Sun October 16, 2011

It breaks my heart to see the trees dying.  Trees define a temperate climate; there are no majestic trees in the desert.  Golden brown grass has a certain stoic beauty because we know that when at last it rains the grass will turn green again.  But when hundred year old trees die, they will not be restored by a little shower.

The heat may have let up, and we have even had a bit of rain, but it is unlikely that the extraordinary drought is over.  Did you know that nationwide, 50 to 70% of municipal water is used to irrigate home landscapes?  In Georgetown and Round Rock, that means that water is imported from Stillhouse Hollow, treated to be safe enough to drink, pumped to our houses using electricity, and then thrown on the grass.  What if this is a multi-year dry spell?  Are there ways that an individual could use water more effectively?  Could we still have trees?

People are starting to talk about graywater.  Graywater is water that has already been used in a home’s washing machine, showers and tubs, and bathroom sinks.  It is called graywater because it is not as contaminated as blackwater, which has been flushed down the toilet.  Water from the kitchen sink and dishwasher is also considered blackwater because of the large amount of food waste that may be present.  In some areas where drought is a way of life, graywater is used to flush toilets, but that requires some very sophisticated plumbing.  The most common use of graywater is to irrigate plants.

Paolo Pinto directed on-site sewage facility inspections for the Williamson County Health Department for 18 years, so he knows quite a bit about dirty water.  He has been using graywater on his trees and vegetable garden since his house was built in 1986.  Paolo has a large lot in the Chisholm Trail Utility District, which has been under severe watering restrictions all summer.  Although most of his neighborhood is wooded with native trees, the elms are wilting, and the live oaks don’t look so good either.  All is not lost though, because there is one factor working in favor of the trees:  Paolo’s graywater system.

Paolo’s shower and washing machine do not drain into his septic system.  Instead, they drain into a 50 gallon tank buried in his backyard, and from there by gravity into a hose that he can move from tree to tree as needed.  An eight minute shower uses about 20 gallons of water.  An average top-loading washing machine uses 41 gallons of water per load.  A bathroom faucet produces about 2 gallons per minute.  Excluding the blackwater going down the toilet and kitchen sink, an average American produces about 40 to 50 gallons of graywater every day.  An established tree needs approximately ten gallons of water per inch of trunk diameter every week, so if Paolo generates 50 gallons of graywater a day, he could water a different 5 inch diameter tree each day of the week.

Paolo is quick to point out that his graywater system would not comply with current state laws if it were being built today.  One new requirement is that a system must allow 100% of the graywater to be diverted into the sewer or septic system if necessary.  This is a very logical requirement.  If the ground is soggy from heavy rains, you would want to be able to turn off graywater irrigation.  Or what if there is a baby in the house and dirty diapers are regularly being washed?  Nobody wants diaper water going onto the lawn.

Another state regulation is that the graywater must not be sprayed and must not be allowed to pool or run into a neighbor’s yard, the street, or a natural body of water.  Care must be taken to avoid creating breeding habitat for mosquitoes.  The plumbing that carries graywater must be clearly distinguished as non-potable water, usually by making the pipes purple and posting signs.

Graywater does not adapt well to soaker hoses or drip irrigation because it has a lot of particles and lint that rapidly clog the openings.  Graywater should not be stored in a tank for more than 24 hours, because it contains soap, bits of food, and bacteria, so if it sits around it will stagnate into blackwater and it will stink.

The most effective (and lowest maintenance) graywater systems disperse the water underground as soon as it is generated into a mini drain field where trees are planted.  An anonymous city inspector told me that he has had an underground graywater system irrigating a row of peach trees for years and they look fantastic, even with no additional water this summer.  He does have to be careful about what kind of laundry soap he uses.  Most powdered laundry detergents are high in sodium, which can be harmful to plants.  Borax can also kill plants in even small quantities.  Once his wife got enthusiastic with bleach in the white loads and wiped out a big area of grass.  He also told me that currently there are no City of Georgetown regulations about graywater systems.  As long as the neighbors aren’t disturbed, the code enforcers won’t concern themselves with your laundry water.  Residential codes for graywater may be adopted in the future, but we don’t have them yet.

A graywater system can be a useful way to conserve water, but it is more complicated to install than it sounds, and there is a lot that can go wrong.  Before installing a system, figure out how much graywater your household would produce and how you would use it.  Consult with a plumber.  And don’t feel guilty if it just sounds like too much trouble.  Even if you don’t take advantage of your graywater, the city is already recycling it.  Treated effluent (cleaned up sewage) is used to irrigate the local golf courses.

A useful internet resource for graywater systems is Oasis Design, a California company that has been designing sustainable water and wastewater systems for many years.

Solar Water Heating

Published in the Sun October 1, 2011

In my yard is a large black garden hose.  On a sunny day, the water that comes out of that hose is as hot as coffee.  My plants don’t really appreciate the hot water, but it does make you think about the excessive solar energy that has lately been falling on us like a plague, and how it might be put to a useful purpose.

Back in 1891, when people still heated their weekly bath water on a wood stove, Clarence Kemp patented the first commercially available solar water heater.  The Climax Solar Water Heater consisted of a pine box, lined with black felt and covered with a pane of glass.  Inside the box were four iron tanks, painted black, which held a total of 32 gallons of water.  The Climax would be installed on a south facing roof and plumbed into the bathroom.  Mr. Kemp’s advertisement warns that under very sunny conditions the water almost boils.  With this contraption the lucky owner could “go home at night and find hot water for bath ready for you, on tap same as cold water… There is no delay and no expense for fuel.”

Over the next 30 years, many thousands of solar water heaters were installed in California and Florida, but by the 1930s the widespread availability of natural gas (and its subsidized low cost) killed the market for solar hot water.  The idea didn’t go away though.  In 1979, in a show of support for alternative energy, Jimmy Carter installed 32 solar collectors on the roof of the White House to provide hot water for the staff cafeteria.

Only five years later, Jeremy and Linda Gambell began building a home in Georgetown.  The cheapest option for water heating would have been natural gas, but the Gambell’s subdivision did not provide natural gas, so they were faced with a choice between the hassles of propane or the expense of electricity.  As newcomers from the snowy regions of New York, the Gambell’s were impressed by the reliability of Texas sunshine.  Or maybe they were just hippies, but they decided to buck the system and try solar water heating.

The water heater that Jeremy chose had advanced a long way beyond the Climax Solar Water Heater.  There are two 4x8 foot collector panels on his roof.  From the driveway they look almost like skylights.  Circulating through the collectors is a 50% propylene glycol solution, a foodsafe antifreeze.  The glycol is heated by the sun and is then pumped through a heat exchanger where it transfers the heat to the household water, which is stored in a regular 120 gallon hot water tank.  The water can stay hot in the insulated tank for several days.  A thermostat on the tank allows for back-up heating by electricity should the collectors fail to provide enough heat, such as might happen when we have several days in a row of cloudy weather.  It is not necessary for the weather to be hot for the panels to work.  A cold sunny day can heat water, just like the inside of your car can become quite warm even in the winter.

I asked the Gambells if they really have enough hot water.  Linda looked askance at Jeremy and said, “Well, there was that time you forgot to turn the breaker back on in the fall.”  It turns out that every spring, Jeremy turns the back-up electric water heater completely off, and doesn’t turn it on again until about November.  In other words, for most of the year, they don’t even use the back-up electricity at all; the solar collectors supply 100% of their hot water.  I was a bit incredulous.  Surely they must take their showers at night and just didn’t notice that the water was cool in the mornings?  Nope, they both take showers AND they do the laundry in the morning, and all through the hot season they have plenty of hot water.  Linda says she never worries about running out of hot water, but with the drought she does sometimes worry about running out of cold water.

The Gambells paid $3955 for their hot water system in 1985.  Every two years the “Solar Man” comes and changes the glycol solution for $42.50.  I recently bought a similar system and mine cost $4830, including the tank and installation.  There is a 30% federal tax credit, bringing the net cost down to $3381.  Mine won’t need the glycol exchanges, because it uses distilled water in the collectors.  If you would like to estimate your own return on investment in a solar water heater, there is an excellent lifetime cost calculator at www.solar-estimate.org that lets you plug in the rate you pay for electricity and the number of people in your family.  To make a long story short, by reducing electricity costs, a solar water heater will pay for itself in 4-10 years, depending on how much hot water you use and how fast electricity rates go up.

On average in the US, water heating accounts for 14% of total household energy consumption.  In a large family, the annual carbon dioxide emissions of the water heater can equal those of the family automobile.  The sun is going to shine on us anyway; we should put it to work.