Date of Award

2026

Document Type

Honors Thesis (Open Access)

Department

Colby College. Environmental Studies Program

Advisor(s)

Gail Carlson

Second Advisor

Philip Nyhus

Third Advisor

Manny Gimond

Abstract

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative, and toxic contaminants that have contributed to widespread environmental pollution in Maine. This study examines the distribution of Earthlife®, a composted Class A biosolids product produced at the Hawk Ridge facility in Unity, Maine, and evaluates associated PFAS contamination in compost and surface waters. Maine Department of Environmental Protection records from 2014-2021 were used to map 1,977 Earthlife delivery records across the state, revealing widespread distribution concentrated in southern and central Maine and extensive redistribution through intermediary recipients, which accounted for approximately 48% of the total compost volume delivered. Compost testing across multiple sampling events (2018-2025) confirmed PFAS contamination in Earthlife products ranging from 102-892 ng/g, although PFAS analyte patterns varied substantially over time. Surface water sampling at eight locations near the Hawk Ridge facility in Unity showed elevated PFAS concentrations (25-1681 ng/L), among the highest reported in Maine surface waters. PFAS were detected in all surface waters sampled at Colby College in Waterville, Maine, where Earthlife delivery during baseball field construction was documented, with the highest concentrations in detention ponds nearest the probable area of compost application (317.9 ng/L). Although elevated PFAS contamination was associated with documented Earthlife delivery areas, incomplete tracking of final application locations and overlapping contamination sources prevented attribution of contamination solely to Earthlife compost.

Keywords

PFAS, pollution, compost, biosolids, Class A sludge, surface water

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