Introduction

The waste sector is an increasingly important component of greenhouse gas (GHG) inventories driven by rapid urbanisation. Particularly for a state like Goa, where tourism driven economic activities and rising consumption patterns significantly influence waste generation. Unlike other states that struggle with gaps in activity data, Goa stands out with relatively better data availability.  This includes data related to municipal solid waste and recycling records to hazardous-waste annual reports and facility-level operational data.

This assessment is a part of a broader process of preparing a GHG emission inventory along with assessing the quality of available data for the state of Goa.
However, the major challenge is that the available data is not organized or reported in formats compatible with IPCC guidelines. This misalignment makes it difficult to calculate accurate emissions from the waste sector, limiting the ability to assess its true contribution to the state’s total GHG emissions. 

In the  IPCC Guidelines, the waste sector classified as the fourth sector is defined as materials that are discarded, intended to be discarded, or required to be discarded and are accounted for under GHG emission inventory. The Waste sector is comprised of four sub-sectors;

• 4A Solid Waste Disposal

• 4B Biological Treatment of Solid Waste

• 4C Incineration and Open Burning of Waste

• 4D Wastewater Treatment and Discharge

This article outlines the key data requirements for the sub- sectors, based on the Annex 1 Worksheets and practical steps that government departments can follow to ensure comprehensive GHG estimation for the waste sector in line with the IPCC Guidelines.

4A Solid Waste Disposal

Goa has operational municipal solid waste (MSW) data currently available, such as daily quantities of wet waste, dry waste, mixed waste, and tree waste processed at facilities available through Goa waste management corporation (GWMC). This provides an excellent understanding of waste flows in the state but unfortunately does not directly align with the activity data requirements of the IPCC Waste Model (MS Excel) used for estimating methane emissions from solid waste disposal sites.

The IPCC Waste Model (MS Excel) requires very specific inputs, such as: 

1. Waste Generation by Waste Type (composition %) :

• Food waste

• Garden waste

• Paper

• Wood/straw

• Textiles

• Nappies

• Sewage sludge

• Industrial waste

2. DOC (Degradable Organic Carbon) values

• Weight fraction per waste type

3. Methane generation rate constant (k)

• Depends on waste type & climate (wet/temperate).

4. Deposited MSW in landfills per year

However Goa’s MSW dataset is aggregated into broad operational categories that must be further disaggregated and mapped to IPCC defined waste types. Additionally, only the fraction of waste that is ultimately deposited in landfills after processing, recovery, or RDF generation should be included in the calculations. Therefore, while Goa’s existing data is valuable, it requires reclassification, waste composition information, and annual landfill deposition estimates to be compatible with IPCC methodology to calculate emissions from solid waste disposals.

4B Biological Treatment of Solid Waste

Estimation of CH₄ emissions from the Biological Treatment of Solid Waste, were calculated using anaerobic digestion type of treatment and IPCC dry weight factors. Annual treatment data was available only for the Saligao plant taken from Goa Waste Management Corporation, based on organic fraction data (from 2019) and organics from dry waste (from 2022). However, the facility does not specify the types of waste treated, limiting the use of waste specific IPCC factors.

Due to the absence of data on methane recovery and flaring (assumed to be practically absent), only gross methane emissions have been computed and net emissions were not estimated. Further, N₂O emissions were also assumed negligible for anaerobic digestion. There are no operational data for the other facilities (Cacora, Bainguinim, Verna) present.

4C Incineration and Open Burning of Waste

The calculations for this sub- sector are based on waste incineration data reported in the Goa Pollution Control Board’s Hazardous Waste Annual Report. For the Waste Incineration category (4C1), CO₂ emissions were calculated using the quantity of waste incinerated as reported by the Goa Pollution Control Board, together with IPCC default factors for dry matter content, carbon content, fossil carbon fraction, oxidation factor, and molecular conversion values. These inputs allowed estimation of CO₂ emissions from incineration and CH₄ emissions from incineration. However, the calculation of N₂O emissions from incineration could not be completed because the IPCC Guidelines do not provide a default emission factor for N₂O from waste incineration, and no India specific emission factor is available in national inventory literature. Additionally, calculations for open burning of waste were not undertaken, as there is no reliable data on the quantity of waste openly burned in Goa, and therefore no basis for applying IPCC default open burning emission factors.

4D Wastewater Treatment and Discharge

To calculate the organically degradable material in Domestic waste water (4D1), only some of the IPCC required data is available. Using Goa’s population (2013–2023) and the IPCC default of 34 g BOD/person/day, we could estimate the total organic load.

However, CH₄ emissions could not be calculated. Goa does not have state wide data on treatment systems, and the limited Central Pollution Control Board information shows only aerobic STPs, all with an IPCC MCF of 0, which leads to an emission factor of 0 and stops further CH₄ estimation.

The calculation of net CH₄ emissions based on the income group method is also not possible, since there is no data on which income groups use which disposal methods, nor any information on sludge removal or methane recovery. Additionally, calculations for nitrogen in effluent and indirect N₂O emissions could not be carried out because the required data is unavailable.

For industrial wastewater treatment (4D2), almost all the activity data required by the IPCC is missing. To estimate the total organic degradable material in wastewater for each industry sector, we would need information on industry sectors, their production levels, wastewater generated, and COD values. Since none of this data is available, these calculations cannot be done.

We were able to identify the types of industrial treatment systems from the website of Goa Vidhan Sabha, and using IPCC defaults for maximum CH₄ producing capacity and MCF values, the emission of CH4 for industrial waste water could be calculated. But to estimate actual CH₄ emissions from industrial wastewater, we also need data on organic load, sludge removal, and methane recovery for each industry none of which is available.

Conclusion/Key recommendations

To strengthen Goa’s GHG emission inventory, it is crucial to reorganize existing data and establish a standardized, IPCC aligned approach to waste sector reporting. The following departments play a significant role in this process :

• Goa State Pollution Control Board (GSPCB)

• Goa Waste Management Corporation (GWMC)

• Urban Local Bodies and Village Panchayats

• Directorate of Municipal Administration (DMA)

• Public Works Department – Sewerage & Water Supply

• Directorate of Health Services (for biomedical waste)

• Goa Industrial Development Corporation (GIDC)

These departments could adopt uniform data collection protocols, maintain annual records consistent with IPCC Guidelines and the 2019 Refinement, and ensure regular data sharing. Strengthening coordination and establishing clear reporting responsibilities across these departments will significantly improve the accuracy, completeness, and reliability of Goa’s climate action framework.