Compost Use in City of LA: Updated Model Water Efficiency Landscape Ordinance (MWELO) In Practice

Global Green is working on modeling scenarios for compost use in order to determine pathways through which more soils can receive the benefits of compost in urban and suburban areas.

One way that this happens is via ordinances, such as the Model Water Efficient Landscape Ordinance in California.


What is the Model Water Efficient Landscape Ordinance?

The 2015 update of this ordinance requires compost use in soil for irrigation & landscape design plans to improve water efficiency.

Commonly known as the “MWELO”, the Model Water Efficient Landscape Ordinance promotes water efficient landscapes in new developments and retrofitted landscapes. It is designed to use California’s limited water supply in an efficient manner for landscape irrigation.

Timeline of the MWELO update process:

  • April, 2015: California Governor Jerry Brown Executive Order B-29 required the update of the MWELO by California Department of Water Resources (CDWR) in response to severe local unprecedented drought to achieve 25% reduction in water use.

  • December, 2015: New MWELO requirements went into effect.

  • March, 2016: Deadline for local agencies, both cities and counties, were expected to adopt the updated version of the ordinance MWELO.  

  • January, 2017: Start date for annual reporting on MWELO implementation by local agencies.

Learn more about the MWELO ordinance in a previous article on this topic:

Compost Could Create Water Efficient Landscapes in California


What does it have to do with compost?

Some of the key changes of the updated MWELO concern water efficiency and the required integration of compost.  

Compost has enormous drought relief benefits, and thus, water conservation potential in soil amendment. Indeed, its greatest benefit to the landscape sector is its ability to conserve moisture which reduces water consumption and related costs. Research completed in the US and abroad proved that soil amendment can reduce the water need for irrigation by 25% to 50%.

Therefore, compost is a key element of the “watershed approach” of the MWELO update.

MWELO applies to the following landscape projects:

  • NEW construction with a landscape area of 500 square feet or more

  • A rehabilitated landscape project of 2,500 square feet or more

Under both landscape and irrigation design plans sections, the MWELO requests the following for eligible projects:

  • A minimum 6% organic matter content of soil  in the top 6 inches of soil

  • If not possible, a minimum compost incorporation rate of 4 cubic yards per 1,000 square feet at a 6 inches depth into the soil

  • The compost use features must be provided on plans

The use of compost results in numerous environmental benefits which make it a valuable sustainable material for climate change mitigation, such as:

  • Soil health quality increase

  • Plant growth increase

  • Carbon sequestration.


What is the link with Global Green’s work?

In 2016, the Coalition for Resource Recovery (CoRR) team at Global Green implemented a Food Waste Reduction and Recycling program engaging more than 523 households in 10 cities across California to combat food waste. More than 84,000 lbs of food waste were successfully diverted from landfills, avoiding harmful greenhouse gas emissions (mostly carbon dioxide and methane).

Recently, we published a Multi-Family Units/Apartment Guide to Compost Use. Practices for landscaping and the use of compost as soil amendment vary widely among public and private sector real estate actors. Ordinances like MWELO represent an opportunity for greater use of compost and the associated benefits.

What do the impacts of MWELO implementation re: compost use look like in real life conditions?

The City of Los Angeles adopted the updated MWELO on December 1st, 2015 through the Municipal Code (LAMC), under the Green Building Code;  This means only building projects falling under the Green Building category must comply with the MWELO requirements. It must be emphasized that the U.S. Green Building Council’s Leadership in Energy & Environmental Design (LEED) certification is a voluntary initiative.

In the year 2016, between 60% to 80% of all building projects in City of Los Angeles were green buildings with compliance inspected by the Green Building Division of the Los Angeles Department of Building and Safety (LADBS).

Among all the projects falling under the green building inspection this same year, about 13,700 of them complied with MWELO, accounting for a total landscape or project area satisfying MWELO of around 88,889 square yards.


What does this mean for soil amendment in the city?

The 88,889 square yards of project area in 2016 represents a significant compost use volume of 15,111 cubic yards, when considering the MWELO requirement of 6 inches depth compost incorporation into the soil.

Based on the MWELO’s 6% organic matter requirement of soil amendment, the 15,111 cubic yards of compost/ soil amendment incorporated into project area soils in 2016 translates to approximately 907 cubic yards of organic matter in City of Los Angeles soils. Given this estimated organic matter within amended soils, and that by weight, one cubic yard of compost weighs approximately 40 tons, 36,280 tons of compost is estimated to have been utilized throughout the city in 2016.

  1. 6 inches = 0.17 yards (88,889 square yards * 0.17 yards) = 15,111 cubic yards

  2. (15,111 cubic yards * 0.06) = 907 cubic yards


  4. 40 tons compost per cubic yard [907 cubic yards *(40 tons/cubic yard)] = 36,280 tons

With the continued support from the Walmart Foundation, Global Green was able to analyze Food Waste Solutions

With the continued support from the Walmart Foundation, Global Green was able to analyze Food Waste Solutions

Amandine Chaleil