Biodegradable nanofibers have emerged as a promising solution for sustainable air filtration, addressing growing concerns about plastic waste and environmental persistence of synthetic filter materials. These eco-friendly alternatives, including polylactic acid (PLA), cellulose, and starch-based nanofibers, offer comparable filtration efficiency while ensuring reduced environmental impact through natural degradation pathways. The development of such materials aligns with global efforts to minimize microfiber pollution and transition toward circular economy principles in filtration technologies.

Fabrication of biodegradable nanofibers primarily relies on electrospinning and solution blow spinning techniques. Electrospinning remains the most widely used method, producing fibers with diameters typically ranging from 50 to 500 nm through the application of high voltage to polymer solutions. For PLA nanofibers, optimal results are achieved using chloroform and dimethylformamide solvent systems with concentrations between 8-12% w/v, yielding uniform fibers with adequate mechanical properties. Solution blow spinning offers advantages in scalability and production rate, particularly for cellulose acetate nanofibers, where production speeds can reach 10-20 times faster than conventional electrospinning. Both methods enable control over fiber morphology, porosity, and web density—critical parameters determining filtration performance.

Mechanical strength remains a key consideration for biodegradable nanofiber filters. PLA nanofibers exhibit tensile strengths between 2-4 MPa, while cellulose-based variants demonstrate slightly higher values of 3-5 MPa due to their crystalline structure. These values remain lower than synthetic counterparts like polyacrylonitrile (8-12 MPa) or polyvinylidene fluoride (10-15 MPa), necessitating reinforcement strategies for certain applications. Crosslinking with citric acid or glyoxal improves wet strength for cellulose nanofibers by 40-60%, while composite approaches incorporating nanocellulose or chitin nanowhiskers enhance PLA's mechanical properties without compromising biodegradability.

Degradation mechanisms vary significantly among biodegradable nanofiber types. PLA undergoes hydrolytic degradation initiated by water absorption, followed by random chain scission, with complete mineralization requiring industrial composting conditions (58°C, high humidity). Cellulose nanofibers degrade through enzymatic action by cellulases present in soil and aquatic environments, showing 60-80% mass loss within 90 days under natural conditions. Starch-based materials demonstrate the fastest degradation rates, with complete breakdown occurring within 30-45 days in active soil, though this compromises their durability during use. Environmental factors such as pH, microbial activity, and temperature dramatically influence degradation kinetics, requiring careful material selection based on intended filter lifespan.

Filtration performance comparisons reveal trade-offs between sustainability and efficiency. Biodegradable nanofiber filters typically achieve 95-99% efficiency for PM2.5 particles at pressure drops of 100-150 Pa, comparable to synthetic nanofiber filters. However, their quality factors (QF), which account for both efficiency and air resistance, tend to be 10-15% lower due to higher fiber packing densities needed to compensate for mechanical limitations. Cellulose nanofiber filters modified with TEMPO oxidation show exceptional performance for nanoparticles below 100 nm, capturing 99.9% of particles at 200 Pa due to enhanced surface charges. For microbial filtration, chitosan-functionalized PLA nanofibers demonstrate superior antibacterial properties while maintaining 97% efficiency for bacterial aerosols.

Industrial adoption faces several technical and economic challenges. Production costs for biodegradable nanofibers remain 20-30% higher than synthetic alternatives, primarily due to lower production volumes and more complex solvent recovery systems. Scaling up electrospinning processes while maintaining fiber uniformity requires significant energy inputs, with current industrial systems consuming 5-8 kWh per kilogram of produced nanofibers. Solution blow spinning offers better energy efficiency at 2-3 kWh/kg but faces limitations in producing sufficiently fine fibers for high-efficiency applications. Additionally, the hygroscopic nature of many biodegradable polymers complicates storage and handling in industrial settings, requiring controlled humidity environments below 30% RH.

Lifecycle assessment studies provide quantitative comparisons of environmental impacts. Cradle-to-grave analyses show that PLA nanofiber filters generate 60% less fossil fuel depletion and 45% lower global warming potential than polypropylene filters of equivalent performance. Cellulose nanofiber production demonstrates even better outcomes, with 80% reduction in cumulative energy demand when utilizing agricultural waste feedstocks. However, water consumption during cultivation of biomass raw materials remains a concern, particularly for starch-based systems requiring 20-30% more water than petrochemical alternatives. End-of-life scenarios significantly influence overall sustainability, with industrial composting offering the best environmental outcomes but limited by infrastructure availability.

Material innovations continue to address performance gaps in biodegradable filtration. Hybrid systems combining PLA with polyhydroxyalkanoates (PHA) achieve better mechanical stability while maintaining compostability, with Young's modulus improvements of 30-40%. Bacterial cellulose nanofibers produced through microbial fermentation exhibit exceptional purity and uniformity, reaching filtration efficiencies of 99.97% for 0.3 μm particles—performance matching HEPA standards. Surface modifications using green chemistry approaches, such as enzymatic grafting of hydrophobic moieties, enhance moisture resistance without compromising biodegradability, extending functional lifetimes in humid environments.

Standardization and certification present additional hurdles for widespread implementation. Current test methods for biodegradability (ASTM D6400, EN 13432) require modifications to account for nanofiber-specific behaviors, particularly regarding nanoparticle release during degradation. Regulatory frameworks struggle to classify these materials appropriately, caught between definitions of manufactured nanomaterials and natural fibers. The development of industry-specific standards for biodegradable air filters remains in early stages, with only preliminary guidelines from organizations like the International Organization for Standardization (ISO) addressing nanofiber-specific concerns.

Future directions focus on closing performance gaps while maintaining environmental benefits. Multilayer filter designs combining different biodegradable materials optimize both mechanical support and filtration efficiency, with pilot studies showing 15% improvement in quality factors. Advanced fiber alignment techniques, such as magnetic-field assisted electrospinning, enhance particle capture efficiency by 20% through controlled pore structure design. Research into marine-degradable formulations addresses concerns about filters entering aquatic ecosystems, with promising results from alginate-based systems showing complete seawater degradation within 120 days.

The transition to biodegradable nanofiber filters represents a complex balance between technological performance, economic viability, and environmental responsibility. While current solutions may not yet match all performance metrics of synthetic alternatives, their rapid development and improving characteristics position them as essential components in sustainable air filtration systems. Continued advancements in material science, coupled with supportive policy frameworks and industrial commitment, will determine the pace at which these eco-friendly alternatives can replace conventional filtration media across various applications. The integration of circular design principles—from raw material sourcing to end-of-life management—will be crucial for realizing the full potential of biodegradable nanofibers in creating truly sustainable air purification technologies.