Who we are

Yellow Tree is passionate about the environment and about serving others. We are a team of engineers and environmental scientists that specialise in stack emissions testing, and we love our work.

Who we are

Our awesome staff are here to serve.

Jess Ritten

Jess Ritten

Project Manager

BSc Genetics

Jess is a shining star! Her remarkable intellect and rock-solid work ethic ensure that our clients love her to bits. She heads up our consulting division and serves clients by taking care of Atmospheric Emissions Licenses, NAEIS submissions etc.

Matthew Mwepu

Matthew Mwepu

Lead Scientist

NDip Mech Eng

Matt is our most experienced stack tester. With a wealth of knowledge spanning the testing of all emissions from particulate matter through to dioxins and furans, Matt is our guy! We love his confidence and bold leadership!

Rumbi Zireva

Rumbi Zireva

Laboratory Manager

BSc Chem Eng, MSc Med Eng

Rumbi’s work is outstanding! As a talented young chemical engineer (with a Masters degree!) she heads up our laboratory, audits our compliance with the US EPA stack testing methods and is working towards our ISO 17025.

Paul O'Brien

Paul O'Brien

Equipment Manager

BSc Environmental Science

Paul is insightful. He has worked in most areas of Yellow Tree as it has grown, and his incredible talent is put to use managing Yellow Tree’s scientific equipment, calibrations and overseeing daily site protocols. Paul is a legend at Yellow Tree.

Mntungwa Mabusela

Mntungwa Mabusela

Assistant Scientist

NDip Chem Eng

Mabu is our in-service trainee from CPUT! He is sharp and learning fast. He is also quick to laugh and to keep the spirits high. Stack testing is a tough profession, and Mabu makes light work of it.

Bertus Bonthuys

Bertus Bonthuys

General Manager

BSc Mech Eng

Bertus is a great leader! As General Manager he oversees the team, assists key clients, and maintains the high energy environment and client-centric approach that we feel characterises Yellow Tree.

Luka Mayekiso

Luka Mayekiso

Lead Scientist

NDip Chem Eng

Luka is our bright new star! His energy, charisma and outstanding communication make him an asset on site where conditions can be tough and optimism is essential. We are so grateful to have him in the team!

Thanushri Pather

Thanushri Pather

Commercial Manager

BSc Chem Eng

Nush’s energy is contagious. As our Commercial Manager, she engages with clients to establish their needs and to issue proposals. She also seeks out new business and is a technical sounding board.

Sean Charteris

Sean Charteris

Managing Director

PR Chem Eng

Sean is a professionally registered Chemical Engineer with a wealth of experience in combustion, energy generation and industrial emissions. He is passionate about the environment and loves people.

Sakhumzi Baliso

Sakhumzi Baliso

Lead Scientist

NDip Analytical Chemistry

Sakie is one of our best! He has headed up our laboratory, trained younger team members and grown into one of our finest stack testers. He embodies the culture of Yellow Tree and his smile is contagious!

Caitlin Morris

Caitlin Morris

Environmental Engineer

BSc Chem Eng

Cait is a superb chemical engineer! She is incredibly bright and her work is flawlessly accurate. Cait has extensive knowledge of the legislation and air pollution abatement. She writes superb reports and helps our clients.

Khumbu Badantswana

Khumbu Badantswana

Lead Scientist

NDip Chem Eng

Khumbu is our genius. He is the first to solve a problem when testing a boiler or process stack. His quietness belies his confidence and his friendliness. We are blessed to have him head up our Johannesburg team.

Ray Slinger

Ray Slinger

Operations Manager

BSc Environmental Science

Ray is effervescently joyful. As Operations Manager, he manages Yellow Tree’s four stack testing teams and health & safety. They say that one should lead with the heart of a servant, and serve with the heart of a king. That is Ray!

Sine Mjali

Sine Mjali

Assistant Scientist

NDip Chem Eng

Sine is a fantastic site support and has also run our lab. While he may have been a rapper in a previous life, he is now a dedicated emissions tester! His faithfulness to the team is highly valued.

Mdu Mpikwa

Mdu Mpikwa

Assistant Scientist

NDip Chem Eng

Mdu faces the toughest stack testing circumstances with a smile and a steady hand. Even the most challenging 12 hour day can not get him down. He is an asset to our team, and a delight to work with.

David Makalu

David Makalu

Assistant Scientist

NDip Chem Eng

David is gentle and his words are well considered. He is methodical in his stack testing work and he provides great support to Khumbu In our Johannesburg team.

NLA Certified

We are certified with the National Laboratory Association of South Africa. This ensures that we are accredited to test your stack emissions. If you would like to learn more, visit the NLA website here.