A "Waste-to-Energy" company is involved in converting non-recyclable waste materials into usable heat, electricity, or fuel through a variety of methods. These methods can include combustion, gasification, pyrolization, anaerobic digestion and landfill gas recovery. The aim is to reduce the volume of waste that goes to landfills, reduce greenhouse gas emissions, and generate sustainable energy.

1. Incineration: This is the most common Waste-to-Energy method currently used. The process involves burning waste at high temperatures to convert it into heat energy.  

2. Gasification: This technique converts organic materials into gases through heat in a low-oxygen environment, creating a gas known as synthesis gas, or syngas. This can be directly combusted or further processed into synthetic fuels.  

3. Pyrolysis: Similar to gasification, this process breaks down organic waste in the absence of oxygen, creating a mixture of gases, liquids, and solid residue. The gases can be captured and used as fuel.  

4. Anaerobic digestion: This biological process uses bacteria to break down organic waste in the absence of oxygen, producing biogas and a nutrient-rich byproduct often used as fertilizer.  

5. Landfill Gas Recovery: Methane gas is produced when organic waste decomposes in landfills. This gas can be captured and used to generate heat and electricity.  

6. Plasma arc gasification: This involves the use of electrically charged gas or “plasma” to break down waste. The result is a gas that can be used to generate electricity and solid waste that can be used to manufacture construction materials.  

7. Fermentation and Distillation: This process essentially ferments organic waste, creating ethanol which can be used as a biofuel.  

8. Thermal Depolymerization: This mimics the natural geological processes thought to be involved in the production of fossil fuels. Under pressure and heat, long-chain polymers of hydrogen, oxygen, and carbon decompose into short-chain petroleum hydrocarbons.  

9. Mechanical Biological Treatment (MBT): This involves a mixture of processes including mechanical sorting and biological treatment. It can lead to the production of a refuse-derived fuel.  

10. Refuse Derived Fuel (RDF): This process involves processing waste into uniform pellets or flakes which can be used in specific burners designed to utilize this fuel safely and efficiently.  Each one of these methods has its own advantages, limitations, and environmental footprints, and the choice of technology often depends on the type and quantity of waste available, the desired energy output, and other local factors.

Waste-to-energy (WtE) processes help with decarbonization by reducing the emissions of greenhouse gases, in particular carbon dioxide (CO2), that are typically generated by the burning of fossil fuels. Here's how it works:  

1. Reduced Methane Emissions: Landfills are a large source of methane, a potent greenhouse gas. WtE technologies can capture and use this gas, which not only reduces methane emissions but also offsets some of the need for traditional fossil fuels.  

2. Fossil Fuel Replacement: WtE produces heat or electricity (or both, in combined heat and power systems). These energy outputs can replace energy normally produced by burning fossil fuels, thereby reducing CO2 emissions.  

3. Waste Reduction: WtE processes significantly reduce the volume of waste – by about 9% for incineration and 6-7% for gasification. This reduction lessens the need for landfills, decreases the methane produced at those sites, and reserves land for more beneficial and less polluting uses.  

4. Circular Economy: In a WtE plant, components of the waste that cannot be recycled into new products are transformed into electricity and heat. This enhances the overall recycling rate and supports a circular economy, reducing the carbon footprint by minimizing extraction and manufacture of new products.  

5. Recovery of Metals: Post-incineration, valuable metals can often be recovered from bottom ash, the non-combustible material left after incineration. This recycling also reduces the carbon impact of mining new metals.  While WtE does also generate CO2 emissions, because the fuels being used are considered to be part of a short-term carbon cycle (i.e., these materials would decompose and release their carbon content in a matter of years anyway), they are typically not counted in the same way as the long-term release of carbon from fossil fuels. However, WtE processes should be used in harmony with waste reduction, recycling, and composting in a sustainable waste management system.

Selecting a vendor in the Waste-to-Energy (WtE) industry is a process that should be approached with a mix of research and pragmatism. Here's a step-by-step guide:  

1. Identify Your Needs: Understand what your company needs in terms of waste management. This may be influenced by the type of waste your company produces, the volume of waste, your geographical location, any waste management regulations applicable to your region or industry, and related factors.  

2. Research: Start by searching for WtE vendors that service your area. Use online resources to build a list of potential vendors. Your research should involve looking at their reputation, track record, the kind of technologies they use, their capacity to handle the volume of waste you produce, and their ability to meet your specific needs.  

3. Check for Expertise and Experience: Check for the length of time each vendor has been in the business, their client base and the feedback from said clients. Vendors who are leaders in their field or have a substantial positive reputation are usually more reliable. Also, ensure that the vendor keeps up with the latest trends and technologies.  

4. Assess Sustainability Practices: You want a vendor that not only helps manage waste but does so in an eco-friendly manner. Check if the vendor uses practices that reduce pollution, promote energy recovery, and make efficient use of resources.  

5. Consultation and Quotes: Once you have shortlisted potential vendors, reach out to them for quotes. These consultations will provide further guidance on which company best caters to your needs. It might be helpful to ask each vendor how they could help you optimize your waste for energy production.  

6. Visit Facilities: If it's possible, make an effort to visit the facilities of each of the shortlisted WtE vendors. This is to ensure that their operations are as efficient and clean as they claim.  

7. Financial Assessments: Besides being a good fit in terms of service capability, the vendor should also present a sustainable financial model - meaning their cost should fit comfortably within the company's budget.  

8. Legal Compliance: It is essential that the vendor has adhered to all relevant regulations and compliance measures pertinent to waste treatment and disposal.  

9. Create a Contract: Once you have decided on a vendor, work together to create a contract that clearly outlines the duties, responsibilities and expectations of both parties.  

10. Monitor and Evaluate: After some time working with the vendor, evaluate their performance, the quality of their services, and the benefit to your company. Make sure the vendor continues to meet your needs in a satisfactory fashion or consider other options.  In summary, prioritizing your needs, doing research, checking for expertise and experience, and carefully considering financial and legal implications are key steps when choosing a waste-to-energy vendor. This process will give your company the best chance of finding a vendor who can assist in your decarbonization efforts effectively.