Microplastic biodegradation on land

Microplastic biodegradation on land targets plastic fragments already dispersed in soil, biosolids and the terrestrial environment — not the recycling of post-consumer plastic products in industrial bioreactors (that value chain is covered in Microbial bioremediation). Wastewater plants remove up to 99% of microplastic from their influent, but the sequestered particles are concentrated into sewage sludge and redistributed to farmland through biosolid application, so the land compartment is where biology must now do the work. A 2026 PRISMA synthesis of 150 studies confirms that polyethylene, polypropylene and polystyrene are the most persistent soil polymers, while a Tenebrio molitor mealworm gut can cut polystyrene molecular weight by 33% within one week, and an Aspergillus-led soil consortium removed 3.71% of low-density polyethylene mulch mass over a 180-day incubation. The field is pre-commercial: every tabled actor is a research institute, and the honest status is high-risk, early-TRL science.

The key directions of microplastic biodegradation on land are:

1. Enzymatic microplastic depolymerization (Enzymatic Microplastic Depolymerization): engineered PETases, cutinases and MHETases that hydrolyze polyester microplastics to recoverable monomers such as terephthalic acid.
2. Plastisphere microbial consortia (Plastisphere Microbial Consortia): indigenous soil and compost microbiomes — Aspergillus, Bacillus, Pseudomonas, Streptomyces — that colonize microplastic biofilms and depolymerize PE, PBAT and PVC.
3. Insect-mediated biodegradation (Insect-Mediated Biodegradation): mealworms (Tenebrio molitor, Alphitobius diaperinus) and their gut microbiota that fragment and partially mineralize polystyrene and polyethylene.
4. Capture-and-degrade composites (Capture-and-Degrade Composites): enzyme- or peptide-functionalized scaffolds that sequester microplastic from water or soil pore fluid and depolymerize it in place.

Sectoral value chain#

[plastic waste] ──> [fragmentation] ──> [weathering] ──> [plastisphere]
                                          │
                                  (UV + biofilm)
                                          │
                                          ▼
[CO2 + biomass] <─── [mineralization] <─────┘

Value chain levels#

Cross-cutting technologies of the sector:

• Engineered PET hydrolases (Engineered PET Hydrolases): PETase, cutinase and MHETase variants improved by directed evolution and ML-guided design.
• Metagenomic plastisphere profiling (Metagenomic Plastisphere Profiling): full-length 16S and shotgun sequencing to identify active degrader taxa.
• Radiolabel mass balance (Radiolabel Mass Balance): 14C-labelled polymer to quantify true mineralization versus fragmentation.

The stack combines protein engineering, soil microbiome ecology and biohybrid materials science to act on plastic that is already dispersed at low concentration in a solid matrix.

1. Engineered polyester hydrolases (Engineered Polyester Hydrolases):
   • directed-evolution and ML-guided variants of PETase, cutinase and MHETase that retain activity on crystalline substrate.
   • case: Portsmouth fusion cutinase doubled depolymerization products on pre-treated textile at ~20% plastic loading; NREL’s Pseudomonas putida channel recovers TPA at over 65 C-mol%.
2. Plastisphere microbial consortia (Plastisphere Consortia):
   • indigenous soil and compost communities — Aspergillus, Bacillus, Pseudomonas, Streptomyces — selected and applied as bioaugmentation inoculants.
   • case: Wageningen’s Aspergillus consortium removed 3.71% LDPE mass (Mw down 17.2 kDa) over 180 days; CSIR-NEERI showed PVC degrades faster in soil than in compost with Bacillus and Streptomyces dominant.
3. Insect-gut and earthworm biodegradation (Insect-Gut Biodegradation):
   • mealworms and their gut microbiota fragment and partially mineralize polystyrene and polyethylene; earthworms amplify degradation mechanically and via gut-redox modification.
   • case: Tenebrio molitor cut polystyrene molecular weight by ~33% within one week of feeding.