The Carbon Cycle

Simplistically, plants use carbon dioxide for photosynthesis, create hydrocarbons and expel oxygen. Animals use oxygen and expel carbon dioxide. There are many other organisms and mechanisms that produce greenhouse gases. In fact, most plants respire and produce carbon dioxide during the night while laying down new roots. So the carbon cycle should be steady state. The problem with fossil fuels is we’re releasing carbon that was stored thousands of years ago. There is a measurable increase of atmospheric CO2 which will not dissipate easily.

The goal of Carbon Block is to create new carbon sinks that will sequester more carbon than it will expel.

Larger Plants

After growing duckweed for a couple weeks, I’m thinking of moving the system to hydroponics so I can grow larger plants. It looks like I need to periodic run a water pump to maintain clear water. The water may as well filter through some rockwool or vermiculite growing plants. Algae and duckweed are listed as some of the top 10 fastest growing plants but this doesn’t mean long term they will sequester the most carbon dioxide. Tomatoes or cucumber vines may sequester more carbon dioxide once they reach a mature growing phase.

This will require periodic replanting instead of duckweed where it proliferates readily and only requires periodic harvesting. Hydroponic planting media is extremely reusable. It only requires some rinsing out before re-seeding. Give me some feedback here or on Kickstarter on what you think.


I/O assignments

I have the STM8S periodically pumping water to the duckweed tank to maintain circulation. I’ve added polyester fibre fill stuffing as a water filter. It looks like algae is making the water cloudy. While this is also a carbon dioxide sink, I think it will eventually kill the duckweed, as they compete for nutrients.

Here’s my preliminary list of I/O (inputs and outputs) for the microcontroller:

Water Pump. I found a $9 water pump with a USB connector, 5 Volt, 55 mA. Still too much current to drive directly from the STM8S so using a 2N3904 transistor to drive it.

LED lights. haven’t decided to go single LED or RGB. There are cool RGB ones for $2.57 that only need 5 volts and a data line input.

Air fan, battery voltage, solar panel voltage.

5 volt temperature transmitter. I’m amazed that the surface mount ones only cost 30 cents. Consider temperature transmitter probes for industrial use are $250 at the Omega website. The same low-cost is seen for gyros and accelerometers which are standard inside any smart phone. Humidity sensors which are not as common are $9.18 but I don’t expect there will be any in the final Carbon Block product.


First Start

Two tanks are growing duckweed. Unfortunately the winter months don’t provide a lot of sunlight but it should be good for running process tests. The STM8S has been chosen for development. Raspberry Pi and Arduino are not conducive to low power solar operation. The STM8S has a low power sleep mode and is 8 bit which will be fine for this application. It is currently controlling a 5 volt, 55 milliamp water pump to provide periodic water circulation.  This board can be bought for about $8.

Paris Accord

With the Paris accord ratified, experts wonder if consumption reduction will allow us to reach the temperature rise targets. It seems strange that the only solution put forward for more carbon sinks is to plant more trees.

Elsewhere aviation experts dread the potential new drones in the air as obstacles. It’s estimated that there are one million drones being given as Christmas gifts this year. Imagine if that was one million square feet of carbon sequestering.

Why Carbon Block?

As my usual mindset, a play on words. Sun block prevents sunburn, carbon block prevents global warming by sequestering carbon dioxide. It’s also a derivative of carbon black. The ultimate machine would be a nano-process that could convert solar energy into carbon, theoretically a carbon block or tower if the process could run forever. This would essentially be photosynthesis without water and deployable in non-arable areas.