Our Team | Material Matters Inc.

Meet the team of project managers, scientists, and specialists who bring their technical expertise and attention to each project.

Chad Harrison, PE

President, Chief Executive Officer

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Chad Harrison, PE

President, Chief Executive Officer

Chad Harrison is an accomplished leader and engineer with 30 years of experience in driving business growth, managing multidisciplinary teams, and delivering innovative solutions. Chad holds a B.S. in Geo-Environmental Engineering from The Pennsylvania State University and is a licensed Professional Engineer in Pennsylvania, Ohio, Maryland, and West Virginia. Throughout his career, Chad has held senior leadership positions in the engineering and consulting industry, overseeing large teams, managing complex projects, and implementing strategies that deliver consistent growth and operational efficiency. His expertise spans technical oversight, business development, and organizational management, with a focus on creating value for clients and stakeholders. As President and CEO of Material Matters, Inc., Chad leverages his extensive experience and leadership skills to guide the company into its next phase of growth and innovation while maintaining a strong commitment to advancing the company’s mission and fostering excellence across all operations.

Lisa Challenger

Chief Operating Officer

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Trudy Johnston

Technical Director, Certified Operator

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Robin C. Brandt, Ph.D., PE

Technical Director

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Rachel Fogle, Ph.D.

Senior Project Scientist – Land Application

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Joseph Tetreault

Senior Wastewater Scientist

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Yinka Adedeji, Ph.D., PE

Senior Engineer

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Yinka Adedeji, Ph.D., PE

Senior Engineer

Yinka Adedeji, PhD, PE is a Senior Engineer with Material Matters, Inc., specializing in wastewater and biosolids projects with a focus on process optimization, advanced treatment technologies, and regulatory compliance. He supports clients in developing practical, data-driven solutions that enhance system performance, improve treatment efficiency, and enable successful project delivery. Dr. Adedeji brings specialized expertise in bioenergy and waste-to-energy systems, including pyrolysis, gasification, anaerobic digestion, and emerging hydrothermal processes such as liquefaction (HTL) and carbonization (HTC). His work emphasizes the integration of resource recovery strategies into wastewater and biosolids management. He applies advanced analytical approaches, including life cycle assessment (LCA), environmental impact evaluation, and net energy ratio analysis—to assess system sustainability and optimize design and operational performance. Dr. Adedeji also brings valuable regulatory insight from his experience with the PADEP, helping clients navigate permitting, compliance, and funding processes.

Phuc H. Vu, PE

Senior Engineer

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Tim Lois

Environmental Scientist III

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Tim Lois

Environmental Scientist III

Tim Lois is an Environmental Scientist III with over 20 years of experience in environmental consulting, specializing in regulatory compliance, biosolids management, emerging contaminants, site assessment, and remediation for industrial, municipal, and public sector clients. Since joining Material Matters, Tim has focused on biosolids beneficial use, permitting strategy, residuals management, and evaluation of emerging treatment technologies and compliance approaches. He brings deep knowledge of environmental regulations, including PADEP Act 2, RCRA, CERCLA, Pennsylvania biosolids permitting programs, and evolving state and federal biosolids requirements, including support for General Permit and Individual Permit compliance strategies. Throughout his career, Tim has managed complex environmental projects from investigation through regulatory closure while coordinating closely with clients, regulators, contractors, and project teams. Tim’s field and leadership experience provides a well-rounded perspective on project execution, including hands-on sampling and operations oversight, permitting support, stakeholder communication, and regulatory navigation. His experience includes large-scale sampling programs, environmental compliance management, corrective action planning, and technical support for biosolids and emerging contaminant initiatives. Tim is recognized for delivering projects on time and within budget while maintaining strong client relationships and regulatory compliance.

Natalie Switala

Senior Wastewater Scientist, Certified Operator

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Ethan Keitel

Environmental Scientist I

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Owen Loper

Civil Engineer Technician

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Nicole Gariepy Morris

Accountant

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Teri Woodings

Administrator

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Samuel Dinner

Software Developer

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Samuel Dinner

Software Developer

Samuel Dinner is a full stack software developer with over a decade of experience designing, building, and deploying production-ready applications. He brings expertise across the entire technology stack, from modern frontend frameworks such as React and Svelte to backend development using Node.js, Python, and relational databases. He is recognized for his ability to deliver scalable, high-performing solutions and modernize legacy systems to improve performance and usability.

Throughout his career, Samuel has developed and maintained complex software applications, led system migrations, and implemented data processing solutions that streamline operations and enhance user experience. His work includes rebuilding administrative platforms with modern interfaces, optimizing backend architectures, and managing production environments to ensure reliability and performance. He has also demonstrated strong initiative through open-source contributions and independently developed applications used by thousands of users. Samuel is proficient in a wide range of programming languages, frameworks, and development tools, with experience spanning frontend development, backend services, database management, and DevOps environments. He holds a Bachelor of Science in Computer Science and applies his technical expertise to deliver innovative, efficient, and user-focused software solutions.