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Hemp in Hempcrete is a GREAT way to lock up CO2. But there's no space to grow enough. Until now.



Hydroponic Carbon Capture (see other proposal) grows stuff really fast, locking-up CO2 in the stuff grown. To KEEP that CO2 locked up, we must inert that stuff long-term.

Hemp is 2nd-fastest growing plant (bamboo #1) so locks-up CO2 really fast. And it can be built with as hempcrete - once cured, embodied CO2 is inerted permanently. Here's AFMPPA's proposal; here's more info.

Main problem is, hemp competes with other land demand for food and biofuel, and loses.

Here's how to beat that.

Much infrastructure is carbon-based, vital,and highly distributed so won't be substituted for decades. That means CO2.

Conventional agriculture is flat, so space-limited; soil loses nutrient, needing clumsy and polluting fertilization, and megatons of valuable water is transpired to atmosphere.

Conventional CCS buries CO2 - expensive, zero payback, and a liability for our kids.

Hydroponic Carbon Capture - HCC - uses captured CO2 to grow stuff - here, hemp - in a soilless enhanced resilient environment, massively accelerating growth and re-absorbing CO2. Crop is protected from pest, disease and weather threat, so higher yield. Stackable system so not space-constrained. Most water is recycled, and closed-loop fertilization = no pollution. It's:

  • Low-tech low-cost. Ambient pressure + temp, simple.
  • Low-risk - established technologies.
  • Failsafe; no pollution, explosion, radiation, bad stuff.
  • Cheap. Prefab "greenhouse" with add-ons. Input heat (mainly) solar; transpired water recovered, recyclable untreated. Plus, EARNS income.
  • Really efficient LOSSLESS agri. Growth accelerated 50% by this LED lighting and 30-40% at higher CO2 levels; may outperform field farming by 80-90%. Immune to pests and weather so may hit >100%. Largely immune to climate change = "future-proof".
  • Carbon sequestration boosting. High efficiency > less farmland needed; "released" land can grow timber, locking-up more carbon long-term (+ wood for "green" construction)
  • CCS compatible - CO2 can come from any source.


Hence, "Hempdroponics".


What actions do you propose?


  1. Agree funding outline for initial research.
  2. Set up a sponsoring university-based project for research to prove concepts and pilot baseline technologies.
  3. Assuming successful, establish suitable funding vehicle to obtain wider income. The nature of the project suggests this would be a combination of government and corporate funding.
  4. Build appropriate expert forum of technical, agriculture and hydroponics experts led by suitable expertise (selected by the forum - must of course also be acceptable to the funding providers)
  5. Move to development stage, recruiting additional resources as required. As details are finalized and designs firm-up, seek further funding perhaps through additional funding vehicles.
  6. Pilot in one or two real-world projects to obtain public buy-in and debug processes and technology.
  7. Roll-out. Low-tech construction demands very simple build skills.



Since rather than being entirely new the design combines existing technologies (see for example this Japanese hydroponic farm and this LED system), by partnering academic and real-world expertise research timescale should be short and move to development rapid.

Initially we must identify and prove key feasibility issues. What growth rate and CO2 uptake is achievable by hemp, by what strain and in what effective volume/area?

It must be stressed that in the absence at this preliminary stage of any design optimization these initial results will probably be far short of what’s possible.


Concept feasibility research in the form of small-scale experimentation should be to establish CO2 uptake and crop yield fed with CO2 levels optimized for the 30-40% yield boost growing under this LED lighting which should improve output by a further 50%.

Increased planting density should also be possible and again needs to be optimized. This article found that higher densities improved the yield of desirable material, and this should be further investigated. The costs analysis below is based on conventional open-field densities, so is quite pessimistic.

This component must generate sufficient data to allow a decision on progress to be taken based on 4 primary criteria:

  • demonstrated agriculture resilience
  • CO2 reduction benefits (overall; resilient agriculture with HCC, plus the effects of usage of the land released for eg timber)
  • crop economics
  • required space/volume (for construction economics)

Assuming overall result to be positive the project can move to the development phase.

RESEARCH COMPONENT RC 2: Hempdroponic unit (HU) design

To consider research required for the HU, it is first necessary to review the HU concept.

HCC may be bespoke build, which may be cheaper where appropriate skills and resources are locally available, or equally to an ISO-container format pluggable modular design, either as converted containers (expensive but excellent logistically) or taking advantage of the established ISO format to develop low-cost lightweight modules that can utilize readily-available handling equipment but without the expense of the "bulletproof" container model.

To worst-case stress-test the concept costings below are modelled on the expensive converted ISO container format. Even then this result in break-even economics; it may well be the case that a lightweight ISO-dimensioned design, or bespoke build, would be significantly cheaper. Consideration should be also be given to 2-dimensional "polytunnel" format where land area and local skills make this more appropriate.

Key benefits of a pluggable ISO-container-dimensioned module design are:

  1. Globally-standardized format, permitting cheap mass-production
  2. User support by a universal maintenance/spares infrastructure.
  3. Easy shipping and handling using universally-available container handling equipment
  4. Very dense storage and installation.

All services (water, nutrient feed, power) would be pre-installed on the module allowing very rapid "plug together" installation of multiple units, even using very low-skilled labor, permitting an installation of any size to be quickly deployed and commissioned.

The design must address parameters of; planting, gas flows, nutrient and water provision, lighting, and crop harvesting. These drive the key research areas.

First is planting optimization and hemp strain selection. Some strains will be more available and grow better than others in different locations.

Current research such as this or this article from on common conventional species indicate that elevated CO2 does increase growth, so combined with this LED option we can expect considerably greater productivity from HCC than from "normal environment" farming.

It should be noted that strain optimization is NOT on the critical path. ALL absorb CO2 and HCC can be initially implemented to grow readily available strains immediately. These can be later substituted by more optimal choices as research identifies these.

Second is gas flow and path. Higher gas flow will have greater turbulence which may improve CO2 take-up; however not every plant is amenable to windy conditions. Designing/controlling the gas path and flowrate to optimize CO2 take-up, especially in a changing and highly-irregular path such as growing plants will create, will be a challenge.

Third is delivery of water and nutrients. These are already well established in hydroponics, and aren’t discussed further here.

Fourth, lighting, is similar to the proposed LED lighting supplemented by ambient light where possible. Implementation of solar power for the lighting, possibly as proposed by Dennis Wilmeth in his proposal "Next Generation Greenhouse" is a given.

The last element is crop harvesting. Key issues will be:

  1. Handling of the crop mass
  2. Access (including height considerations in multi-level HCC)
  3. Crop robustness (to minimise losses in harvesting process)
  4. Working environment (elevated CO2 levels are an unsuitable working environment for humans).


Taking these into account, a “cassette” system is envisaged which addresses all these aspects effectively. The cassette is configured to slot-in to the ISO container format (an equivalent would work equally well in a bespoke build).

It is envisaged that "services" - water/nutrient and lighting - would be part of the container structure. Accordingly the cassette needs to comprise little more than a supporting and handling structure for the crop.

The cassette will be pre-planted with crop seed/seedlings – outside the HU, in a human-friendly environment – then slid into the HU. When the crop was ready to be harvested the cassette would be pulled from the HU, and the crop harvested, the cassette then re-planted and so on.

A cassette system offers many advantages:

  1. It allows for any mix of human labor and automation to handle the cassettes, so is suitable for both high-tech and less sophisticated populations/locations
  2. It would permit a high-density hydroponics installation to be configured similarly to a multi-level high-racking warehouse, with cassettes loaded/unloaded using standard or little-modified warehouse equipment
  3. Pre-planting cassettes greatly reduces non-productive time harvesting and changing-over so yield and CO2 uptake is maximized
  4. A standardized cassette system offers the same standardization benefits as the ISO-container format HU module, as above
  5. The problem of humans working in a high-CO2 environment is removed



The above appears to provide a roadmap to design, prototyping and mass production/roll-out of the system. It should be stressed that this is not intended to be prescriptive of a container system, simply to propose the benefits of this approach should the economics work out.

Who will take these actions?

Initially a sponsor or academic-industrial partnership would need to pick up proof of concept.

Once the potential is demonstrated I would envisage implementation of a funding vehicle (see previous section) for development, this vehicle then growing and being supplemented to move the project forward.

Once development is done and Hempdroponics is real I'd hope that industry, NGOs and governments would pick up and run with the idea on a global scale. The economics and social acceptability should be WAY better than anything offered by the alternatives - especially current "down-a-hole-in-the-ground" CCS - and I believe momentum will simply take over.

Where will these actions be taken?

Can be in any location. Ideally I'd like to see a global project with contributing experts from everywhere. The key word in "global warming" is global - it's everyone's problem and our leaders need to act together.

It's essential we recognize that local factors can affect implementation. It's highly unlikely we can agree on one single model in detail that will work everywhere - ideal hemp strains for example are unlikely to be the same in Russia as in Brazil - but the concept is very portable and should be deliverable in a standardized format to allow the economic and practical benefits - as discussed in previous section "proposed actions"  - of standardization to be leveraged.

Nonetheless, detailed implementation at local level will inevitably differ and the project must not get bogged down - like so many have before - in endless discussion of a "one size fits all" model. That will fail, and will consume valuable time.

How much will emissions be reduced or sequestered vs. business as usual levels?

Hempcrete density 275 kg/m3; 130kg CO2 is captured per m3.

Cement-free hempcrete REPLACES concrete, so 1m3 of concrete (approx 2,400 kg) SAVED. Concrete approx 11% cement; 1m3 concrete = approx 264kg cement.

Best kilns use 3.3 - 3.6 gigajoules to produce tonne of clinker and grind to cement; more typical figure prob. 4-4.5. Say 4; ->1 tonne cement creates ~300 kg of CO2. By replacing 264kg of cement, our 1m3 hempcrete ALSO saves (300 kg/1000 x 264) = 80 kg of CO2 excl. energy/CO2 costs of raw material extraction.

Totalling, 275 kg of hempcrete locks-up 130kg AND substitutes a further 80kg of CO2, total 210 kg (ie 210/275 = 0.75 kg CO2 per kg hempcrete)

Global cement use - concrete - in 2013 = 4bn tonnes. = approx 36 bn tonnes concrete. IF could be substituted only 20% by hempcrete, CO2 locked/saved annually is 5.4 BN tonnes.

Earth has 2.8bn ha available cultivable land. To lock-up 5.4bn tons CO2 @ 208 t/ha (below), need 26e7 ha or less than 1% of this. Stack modules 4 high, need 1/4 that.

What are other key benefits?

  1. Highly resilient, v. efficient agriculture largely immune to climate change, pest, disease, and weather; strongly future-proof
  2. Only needs brownfield land
  3. Frees-up farmland for re-foresting, people, or food
  4. Reduces CO2 emissions
  5. Increased O2
  6. H2O saving - recycles transpired water and prevents it going to atmosphere
  7. Point fertilizing means no run-off pollution
  8. Locking-up CO2 means less CCS needed; extended CCS facility life as fill more slowly
  9. Employment opportunities in clean, green environment
  10. Freeing-up agri land should allow more food to be grown - see also this plan
  11. It's big & visible & VERY green, encouraging belief in benefits of environmental projects which will pave way for other projects.

What are the proposal’s costs?

Stress-test on most expensive (ISO container) option, least productive conventional planting density


Seed: retail $11/lb: say sell $4.42/kg
Hemp Hurds: $5.37/kg., say $2.50/kg
Hemp Bast: $17.64/kg, say $8.50/kg


Conventional field:

Seed yield approx 1t/ha.

Stems approx 7t/ha dry stems, 1: 3 ratio bast:hurds so 1.75t bast, 5.25t hurds.

Field cropturn 90 days. HCC doubles growth rate = 45 day turn, grows year-round; turns p.a. = 365/45 = 8 turns.

Crop height 1m; so 2-tier in ISO container, i.e. 16 crop turns p.a. per unit ground area.

INCOME / hectare (ha):

Crop value based on 16 turns is:

Seed 16 x1 t/ha x $4.42/kg = $70,720/ha

Bast 16 x 1.75 t/ha x $8.50= $238,000 /ha

Hurd 16 x 5.25 t/ha x $2.50 = $210,000 /ha

Total value per ha = $518,720

Carbon credit: 1 ton hemp = 1.63 tons CO2. From above, absorbed CO2 = 16 x (1 + 1.75 + 5.25) t/ha = 128 t hemp /ha @ 1.63 tons CO2/t = 208 t/ha CO2. Carbon credit $2496/ha

Total value per ha = $521,216

INCOME per 40' ISO container:

Footprint = 12 x 2.4 m = 0.00288 ha @ $521,216/ha = $1500 p.a.


Bespoke hydroponic “urban farm” containers (fully-fitted) around $20,000.

But HCC needs no racking (cassette-based) and cheap mass-produced containers. Cost new 40ft shipping container around $2,300; lose security + flooring, bulk-buy ballpark cost ~ $1800

Lighting, irrigation + cassette handling => mass-produced ballpark cost $7000

Cassettes simple frame, est’d $500 per, 4 per container.

Ballpark total container cost $9000.


Capital: Container cost est’d $900,000. Amortize over 15 years = $60,000 p.a


Water transpired & recycled, power solar – ignore for now.

Labour say $40,000 (2 ops).

Nutrient costs: ballpark 30% revenue => $50,000

Total costs ~ $90,000

Revenue $150,000; ballpark profit $60,000 (= amortization)

NET: 128t useful product, break-even with zero subsidy. Locked CO2 = 208t/ha x 0.00288 x 100 conts = 60 tons

By comparison, CCS no useful product, cost est'd at $25-50 per ton CO2

Time line

This is established tech that's simply being brought together, so we should be looking at incremental development only. This should be - and needs to be - fast.


6-12 months to prove feasibility

2 years to develop

5 years to pilot and debug

5 years to build a significant installation. HOWEVER, since modules are common multiple installations can go up simultaneously. Could be operational within a few months of breaking ground, accepting more and more CO2 and generating more hemp for hempcrete as the build extends.

Related proposals

The concept draws heavily upon "Resilient Agriculture with Hydroponic Carbon Capture (HCC)", itself developed from last year's (Finalist) HCC proposal.

It isn't be cheap, and in view of the many benefits offered achieving fast implementation would be a good candidate for funding via my other proposal, in the Global part of the contests, "Quantitative Easing for Climate Change Mitigation + Adaptation"

The "Next Generation Greenhouse" proposal is referred to above and relates to powering the LED lighting used.


Please refer to embedded hyperlinks above.