While most of the coastline was rocky, the 4 coves were
partly sandy. Due to gaps between the rocks, the cleanup
crew was not able to retrieve particles from the rocky
parts of the coastline smaller than approximately 5 cm.
Micro plastics up to approximately 0.5 cm were collected
by hand on the sandy parts of the coves.
Due to transport size constraints, objects larger than 50
cm were omitted from the sample, including nets. The
leftover debris was then randomly split, creating a subsample
of 313 kg, which was then sent to The Ocean
Cleanup.
Concluding, we assume to have collected a representative
North Pacific gyre plastic sample, apart from:
• An underrepresentation of debris smaller than
approximately 5 cm
• Not having included debris larger than approximately
50 cm
• The possibility of (small amounts of) land-based
contamination
• The possibility of the presence of non-floating
and natural debris within the sample.
9.1.3 Sample analysIs
Upon arrival at The Ocean Cleanup in The Netherlands,
the Hawai’i sample was subjected to several analyses
and tests, in order to identify feasible ways of treatment
of this type of debris for maximum recovery of its intrinsic
material value. The Dutch company Recycling Avenue BV
has carried out a general characterization including size
and density distribution as well as material composition.
Subsequently, several analyses were performed to determine
to what extent the polyolefin plastics in the sample
are degraded due to weathering (e.g. UV radiation and
bacterial activity). The degradation tests were carried out
at the Laboratório de Polímeros, Universidade de Caxias
do Sul, Brasil. In addition, SITA Benelux and the Hungarian
company PowerEnergykft carried out tests to produce
pyrolysis oil from the polyolefin plastics