September 16, 2009 | General

Greenhouse Gas Reductions From Organic Waste Digestion

BioCycle September 2009, Vol. 50, No. 9, p. 45
New protocol from the Climate Action Reserve will provide carbon accounting for projects that divert eligible organics to anaerobic digestion.
Max DuBuisson

EMISSIONS from the waste sector have been one of the main targets for greenhouse gas (GHG) reductions. Waste related emissions account for two percent of U.S. GHG emissions, yet many sources remain uncontrolled by regulation or common practice. Such emissions are a prime target for GHG offset projects.
To account for GHG reductions from organic waste digestion projects that cut or prevent methane emissions from the waste sector, the Climate Action Reserve (formerly the California Climate Action Registry) has developed an Organic Waste Digestion (OWD) Project Protocol. The OWD Project Protocol will provide an accurate accounting methodology for GHG reduction projects that divert and anaerobically digest eligible organic waste streams. It will also address codigestion of eligible organic waste streams with livestock manure.
Climate Action Reserve (CAR) expects to adopt the OWD Protocol in October 2009. The protocol will define what types of projects are eligible to receive credit, describe how to quantify emissions reductions and provide guidance for monitoring and verification of projects.

The CAR offset project registry was launched in May 2008 and is a source for voluntary carbon offsets in the U.S. It establishes regulatory quality standards (i.e., rules that follow the same process/procedures as regulatory agencies) for the development, quantification and verification of GHG emissions reduction projects in North America; issues carbon offset credits known as Climate Reserve Tonnes (CRT) generated from such projects; and tracks transaction of credits over time in a transparent, publicly accessible system. CAR is not a trading exchange, but instead an infrastructure for the issuance and retirement of CRTs.
To date, CAR’s adopted protocols address GHG reductions from forest, urban forest, landfill methane (U.S. and Mexico), and livestock methane (U.S. and Mexico) emissions reduction projects. In addition to the OWD Protocol, CAR is developing protocols to address GHG reductions from coal mine methane, ozone depleting substances, and N2O from nitric acid plants.
The process of submitting a project is very straightforward. The CAR system is designed to streamline the complex carbon offset market, making it easier and less risky for project developers to implement emissions reduction projects. The developer opens an account on the CAR system and submits documentation for their project. Upon staff review of the documentation for completeness and general eligibility, the project is publicly “listed” in the CAR system. Once the project has been operational and reductions have occurred and been quantified, the developer hires an accredited verification body to verify the project. The verification documents are submitted to CAR and reviewed by staff. Upon successful completion of verification the project attains the status of “registered,” and the appropriate number of CRTs are issued into the developer’s account. Each CRT is equal to one metric ton of CO2e. Once issued, the CRTs are active credits that can be held, transferred, sold or retired.
There are 95 total CAR projects in 31 states (as of September 3, 2009). Of those, 14 are registered, 65 are listed and 16 are new. The total CRTs issued are 1,622,528.
Public reports are prepared for all CRTs issued as well as those that are retired. Unique serial numbers are assigned to all generated carbon credits, preventing the possibility of double accounting and assuring buyers that when a CRT has been retired, it cannot be sold or transferred again. The public can also view the lists of account holders and projects, along with the supporting documentation for each on the CAR website.


The OWD Protocol is designed to give credit to projects that divert eligible organic wastes from landfills and anaerobic wastewater treatment systems, and send the waste streams to anaerobic digesters. Those eligible organic waste streams are defined as follows:
MSW Food Waste: Food waste commonly disposed into a MSW system, consisting of uneaten food, food scraps, spoiled food and food preparation wastes from homes, restaurants, kitchens, grocery stores, campuses, cafeterias and similar institutions.
Agro-Industrial Wastewater: Organic-loaded wastewater from industrial or agricultural processing operations that “preproject” was treated in an uncontrolled anaerobic lagoon, pond or tank at a privately owned treatment facility. Excluded from eligibility based on CAR’s performance standard analysis are wastewaters produced at breweries, ethanol plants, pharmaceutical production facilities and pulp and paper plants.
Digesters maximize the production of methane from the anaerobic decomposition of the organic waste, and capture the methane gas so that it can be destroyed. The methane destruction can occur on-site or off-site, using a flare, generator, fuel cell, pipeline or CNG vehicle.
As with all methane destruction protocols adopted by CAR, credits are given for the baseline avoided emissions, minus any emissions associated with the project itself. There are four main components involved in determining the eligibility of any particular project:
Location: The project must be located in the U.S. or its territories (versions for Mexico and Canada may be developed at a later date).
Project Start Date: The methane destruction system must have become operational on or after January 1, 2001. However, 12 months after this protocol is adopted, CAR will begin to only accept OWD projects that are submitted within 6 months of their operational start date.
Additionality: The project must meet the performance standard (above and beyond business as usual) and not be required by any federal, state or local regulation.
Environmental Compliance: The project must be in compliance with any and all relevant environmental regulations.
The protocol does not quantify and give credit for any emissions reductions associated with the displacement of grid-connected electricity due to the generation of renewable energy at facilities that use generators or fuel cells to destroy their methane. A flow chart of this GHG assessment boundary can be found in the OWD protocol document (available to download at

Many MSW landfills do not have gas collection and control systems (GCCS), and ones that do are never able to collect all of the gas. By diverting the waste before it reaches a landfill, the organics can be broken down in a closed digester system that has much higher collection efficiency. Credits from these projects are quantified based on the avoided emissions of the landfill.
For jurisdictions that are under a mandatory organic waste diversion target, no credit is given until that target is achieved. At this point, waste diversion is above and beyond that required by regulation. For instance, under California’s Assembly Bill 939, local jurisdictions must meet a target of 50 percent waste diversion. Thus, organic waste will only be credited if originating from jurisdictions that already meet this target without the diversion of the OWD’s project waste. This scenario does not apply to jurisdictions in states with nonbinding diversion goals that do not impose any sort of penalty. There is also consideration for an exception to the regulatory test for projects that divert waste under a local ordinance that is specifically crafted to promote the generation of carbon credits through waste diversion projects.
To quantify the amount of methane that would have occurred had the food waste gone to a landfill (the baseline emissions), a first order decay (FOD) model is used. For each reporting period, the FOD model calculates how much methane the diverted food waste would have produced in the first 10 years after being sent to a landfill. In addition, to create a widely applicable performance standard, the conservative assumption is made that the landfill would have had a GCCS. It assumes that none of the methane is captured from the newly deposited food waste for a period of three years at the landfill, after which point gas is captured at a rate of 75 percent for the remaining seven years. This standardized approach, recommended by CAR’s stakeholder work group, not only assumed that all landfills have GCCS, but also assumed they are operated as if regulated according to stringent federal New Source Performance Standards (NSPS) regulations.
A deduction is taken from this total to account for any fossil fuel or grid electricity consumption needed for waste preprocessing before it enters the digester, as well for postdigester liquid/solid separation or effluent treatment. The fuels used for transportation are not counted since they would have been necessary to transport the waste to the landfill. In many cases, digester facilities are actually located closer to the source of the waste stream, resulting in lower fuel usage for transportation. Also not counted in the assessment boundary are the CO2 emissions from the combustion of methane. These are considered biogenic emissions, as opposed to anthropogenic, and represent the CO2 that would have been emitted during natural decomposition of the solid waste.


It is common practice for municipal wastewater treatment facilities in the U.S. to install digesters and control their methane emissions. However, many agro-industrial wastewater streams continue to be managed in uncontrolled anaerobic lagoons, ponds or tanks. The OWD protocol is designed for these waste streams to be managed in a controlled digester so that the methane may be captured and destroyed. Any wastewater diverted from a treatment plant that already utilizes a biogas control system (BCS) is ineligible for the project.
The protocol relies on three variables to calculate the baseline emissions: the Chemical Oxygen Demand (COD) of the wastewater, representing its organic load; the Methane Correction Factor (MCF), depending on the baseline storage/treatment system; and the methane producing capacity of the wastewater (Bo), which depends on the particular type of wastewater. COD and Bo are based on periodic sampling of the wastewater stream in accordance with guidance given in the protocol. The MCF value depends on what type of system was in place before the BCS was installed.
A deduction is taken if the digestate from the BCS is sent to a landfill for disposal. This calculation uses the same assumptions about the landfill as the calculation for reductions from digestion of MSW food waste, but with different default values.

An important project type eligible under the OWD protocol is codigestion of multiple waste streams in a single digester. These systems can be a very efficient way of treating organic wastes. For projects that include livestock manure mixed with one or both of the waste streams mentioned above, the project developers will use CAR’s existing Livestock Project Protocol for guidance on how to quantify reductions from the manure.
For instance, there are many cases where a dairy farm will have a cheese processing plant associated with it. Waste-water from the cheese plant could be sent to a digester and mixed with manure from the dairy cows, avoiding emissions that would have been released if both of these waste streams were sent to anaerobic lagoons. The OWD protocol would be used in tandem with the Livestock Protocol to quantify the total emissions credits from that project.
The potential number of projects that could use this OWD protocol to earn CRTs is enormous. It will be a valuable tool to incentivize food waste diversion, agro-industrial wastewater processing, and codigestion projects that would not otherwise be possible without the market for the carbon offsets that they generate.

Max DuBuisson is a Business Development Associate with Climate Action Reserve.
Sidebar p. 46
THE goal of the Climate Action Reserve (CAR) is to bring together all relevant stakeholders from a particular sector to work together and develop a regulatory-quality methodology for offset projects to address that sector’s emissions. When determining what emissions to target with a new protocol, CAR considers a number of factors:
Ownership: Is there clear ownership of the emissions reductions? Most CAR protocols target direct emissions reductions. The Organic Waste Diversion protocol is the first to give credit for indirect reductions (the MSW food waste that would have gone to landfills).
Volume: Are there a significant number of reductions to be gained in this industry, either due to large project size or large number of projects?
Solid Science: Is the primary research that is needed for the development of a performance standard robust and complete?
Regulation: Is there clear potential for these projects to pass a test of regulatory additionality, or are this industry’s emissions already highly regulated? Also, is this sector likely to be regulated in the near future, thus limiting the potential for offset projects?
Performance Standard: Is there clear potential to develop a usable performance standard for additional reductions in this industry?
Financial Feasibility: On a lesser scale, it is worth taking a look to see how the costs of implementing these projects compares to the potential revenues to be gained through the sale of credits. If the costs are too high, no projects will be developed.
After collecting the primary research on an industry sector, usually including hiring a contractor for a position paper, CAR holds a public workshop to outline the plans for the new project protocol. All interested stakeholders are encouraged to participate. At that point, an open application period for members of the expert stakeholder workgroup gets underway. This workgroup typically consists of 10 to 20 expert stakeholders of diverse skills and backgrounds who meet periodically and work with the Reserve’s policy team to develop a draft protocol.
Once the workgroup draft is complete, it is posted for a public comment period. These comments are collected, responded to, and incorporated into the protocol as necessary, resulting in a final draft. The final draft is presented to CAR’s Board of Directors for final approval in public session, a unique attribute among nonprofits, after which time projects may be submitted using the new protocol.

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