Skip navigation
Share via:


Fiji has 60 MW of imported fuel diesel. We produce biogas (and fertilizer) from waste & seaweed with engines converted to 70-100% biogas.



(Converting diesels to either 70% CH4: 30% diesel or 100% CH4 is also a subset of two of three concepts the Ocean Foresters are submitting in the Paul G. Allen Ocean Challenge to mitigate ocean acidification.)

Start to eliminate diesel with bi-fuel conversions.  Bi-fuel operation preserves electrical generation reliability as the amount of diesel use fades with improved supplies of natural gas and biogas.

When our other proposals have created a reliable supply of biogas, all the existing generators and the like-new generators can be switched to 100% biogas.  Biogas will become the renewable energy base load and energy storage of a 100% renewable energy electricity and transportation system.   

The developed world has many like-new diesel-fueled emergency generators that are less clean than Tier 4 emissions.  These Tier 0 or 1 units are often replaced to improve reliability or reduce emissions.  (Most emergency generators are operated a few hours each month to ensure reliability.)  The old, but like-new, generators can be converted to bi-fuel (less emissions) and donated to the developing world.  This can be a loosely organized system, like donating your used prescription eyeglasses for reuse.

The emissions from a natural gas or bifuel engine are cleaner than from diesel, as little as half the fossil CO2, near zero particulates, less NOx and SOx.  A biogas engine emits net zero CO2, but biogas must be scrubbed of hydrogen sulfide, to reduce SOx emissions.

There are many unused opportunities to produce biogas (60% methane, 40% CO2) including human and animal wastes, landfills, and seaweed. Much of the developing world lacks wastewater treatment.  Developing country engineers and water pollution regulators have developed biogas and plant fertilizer producing microbial anaerobic digestion systems for human and livestock wastewater treatment.



Category of the action

Reducing emissions from electric power sector.

What actions do you propose?

We can start with the Kinoya Sewage Treatment Plant, on Laucala Bay in Fiji (slide 16).  The Kinoya Sewage Treatment Plant has an anaerobic digester and a biogas flare, but no engine generator.  Kinoya’s digestion could produce sufficient biogas for 500 kW of electricity on average.  The University of the South Pacific’s research using seaweed to produce biogas and fertilizer (Ocean Afforestation) could conduct a trial in Laucala Bay, sharing the flare and possible engine generator.  The Laucala Bay seaweed biogas could grow to produce 6 MW of electricity.

The University of the South Pacific (USP) would coordinate the first bi-fuel engine-generator installation.  USP was instrumental in Kinoya’s flare installation, which was funded through the carbon development mechanism. 

A California city has two spare 2-MW Tier 0 diesel-fueled emergency generators with less than 190 run-hours at their wastewater treatment plant.  (The City would keep their other 2-MW Tier 1 emergency generator, perhaps converting it to bi-fuel.) 

A Fiji-local engine sales or maintenance company (or the electric utility or the wastewater utility) would own and operate the biogas energy production.  For example, the California city has a power-purchase agreement for biogas energy.  The city pays US$67/MWh for the biogas electricity.  A private company owns three engine-generators (total nominal 800 kW) and the biogas scrubbing equipment.

PODenergy could set up a Fiji company to supply the seaweed biogas (and fertilizer) and own/operate the engine-generators.


Ocean Afforestation could replace all Fiji’s 60 MW of diesel-fueled electricity with biogas using about 20,000 ha of Fiji's 40,000 ha of sheltered lagoons. Other small islands have similar proportions of electricity demand relative to their shelter lagoon area.

Other countries will imitate Fiji as fast as their worker training and fuel economics allow.

Who will take these actions?

Most of the continually increasing 20 scientists, engineers, and business people on the Ocean Foresters team are listed in Mark Capron’s profile.

Our team has been working with USP for over a year to move the Ocean Afforestation research project forward.  Other necessary contacts come from our experience helping California wastewater treatment plants toward 100% renewable energy.

Where will these actions be taken?

We start in Fiji and the University of the South Pacific member countries with support from developed countries.  It grows to the Small Island Developing States (SIDS) and larger countries.

We expand to nitrified lakes, lagoons, and bays in Africa, India, China, Chile, Japan, Hawaii, and Mexico.

Eventually, bio-methane from ocean forests of seaweed globally replaces diesel, gasoline, jet fuel, and coal.  (Although the bio-methane may be converted to bio-synthetic liquid fuels to satisfy all energy markets.)


Think beyond reducing emissions!  We need negative emissions.  Replacing diesel with biomethane is part of converting to an Ocean Afforestation bio-methane economy.  Ocean Afforestation can return atmospheric CO2 concentrations to 1900’s levels before 2090 and is explained in Ocean Forester’s related proposals.

In fact, no other reasonably priced technology can scale up to meet the magnitude of the challenge of not only reducing fossil fuel emissions to zero, but also removing nearly 2 trillion tons of excess CO2 in the atmosphere and oceans. Superimposing Ocean Afforestation on McLaren's analysis of other technologies shows this dramatically.

What are other key benefits?

The biogas can be as “free” as other solar and wind energy when it is a by-product of recycling the nutrients from “waste” water for food production.

Imported fuel is replaced with locally-produced fuel generating local and continuing jobs.

The training and skills to operate and maintain a bi-fuel or 100% biogas internal combustion engine or gas turbine is essentially the same as for other similar engines currently used for transportation.

The training to operate and maintain the biogas production and supply will support any use of biogas: fuel cell generators, compression for transportation fuel, conversion to liquid fuel, chemicals or manufactured goods.

Electricity production remains as reliable as the diesel fuel supply and as inexpensive as the biogas supply while the biogas supply increases.  The bi-fuel engine automatically adjusts the diesel fraction, if less natural gas is available.  There is no risk that drops in biogas or natural gas production will stop electricity production.

What are the proposal’s costs?

Nothing.  In countries where diesel fuel costs US$1/liter, the fuel costs alone for a 2 MW Caterpillar 3516 engine-generator are US$0.27/kWh.  (Wholesale diesel by the barge may cost half of retail costs.)  The capital cost for electricity from a biogas fueled engine-generator including biogas scrubbing and California exhaust emissions controls is about US$0.07/kWh.  The biogas produced at the Kinoya Sewage Treatment Plant is currently flared (the fuel is free).  We expect costs less than $0.05/kWh of produced electricity using biogas from seaweed.

Therefore, the reduced fuel cost quickly pays for the project.  Converting a 2-MW diesel engine to bi-fuel in California costs about US$100,000.  We estimate USD $400,000 for an older but low-hours bi-fuel 2-MW engine-generator with gas scrubbing system and electrical connections delivered and installed at Kinoya.

The Fiji electric utility pays US $115/MWh for renewable energy.  The renewable (biogas) energy would be about 9,000 MWh/year, earning US $2 million/year.  The cost of sewage-derived biogas is essentially zero as it is otherwise flared.  The cost of biogas from seaweed may be US $750,000/year initially.  Considering engine maintenance, the simple payback period is less than two years.  This presumes the diesel-fueled fraction is cost neutral with other diesel-fueled electricity on Fiji.

Time line

First bi-fuel engine installed and operating at Kinoya within one year.

60 MW of bi-fuel and 100% biogas engines and seaweed biogas production on Fiji within ten years.

Expanding operations globally at the rate of Ocean Afforestation.

Related proposals

Finalist - Scaling renewables ….  “Fiji, then Indian Ocean Afforestation” highlights the inexpensive renewable energy and food production of ocean afforestation.

Finalist - Agriculture and forestry:Ocean Afforestation” explains using seaweed forests for food, energy, and CO2 storage. 

Finalist - Hydraulic fracturing: “Methane-sniffing drones with distributed mobile sensors!” enables a low leakage methane economy.

Electric power sector: “Replace coal and oil with renewable natural gas (biomethane)” – Ocean afforestation provides sustainable biomethane.

Geoengineering: Withdrew to avoid Negative carbon via Ocean Afforestation being branded with adverse perceptions of geoengineering.

Shifting Cultures ….: “Rapid Planet Change” needs ocean afforestation holistic global ecosystem.

Electric power sector and Fossil fuel sector: “Save the methane!” suggests a carbon fee slows oil drilling while ocean afforestation builds the biomethane economy.



N’Yeurt, A., Chynoweth, D., Capron, M.E., Stewart, J., Hasan, M.. 2012 Negative carbon via Ocean Afforestation.  Process Safety and Environmental Protection 90, 467-474

The above lists 32 references for the calculations involving the Ocean Macroalgal Afforestation ecosystem.  There are seven supplemental information documents, some with more references:

OMA-MacroalgaeProduction&DensityCalcs2012 – 42 references

OMA-ProcessConcepts2012– 2 references

OMA-GlobalCalculations2012,Table2 – 2 references

OMA-AlgalYieldsCalcs&Refs2012 – 45 references

OMA-N2O-EmissionsCalcs2012 – 2 references

OMA-ArtificialGeologicSeafloorStorageOfCO2,2012 – 38 references



Migliore, G., Alisi, C., Sprocati, A.R., Massi, E., Ciccoli, R., Lenzi, M., Wang, A., Cremisini, C., 2012 Anaerobic digestion of macroalgal biomass and sediments sourced from the Orbetello lagoon, Italy, Biomass and BioEnergy 42 69-77