NP-bioTech: catalytic biostabilisation for a fast treatment of citrus pulp or sewage sludge into a rich biofertiliser

Nardo Process bioTechnology
Type of organisation or company
Caltagirone (Catania), Sicily
Language for original content
Key Area
Project elaborated in partnership
district; productive areas; supply chain
Submitted by
ICESP (Italian Circular Economy Stakeholder Platform)
Start/End date

Red Island Srl produces Sicilian orange juice, resulting in large quantities (about 60% of the original weight) of by-product: citrus pulp, consisting of peel, seeds and pulp. Due to its high acidity (pH~3), high moisture content (~85%) and presence of essential oils (d-limonene), a known fermentation inhibitor, citrus pulp is not fermentable. In order to handle this huge amount of biomass, waste and sewage sludge is transformed into organic biofertiliser.

NP-bioTech uses a biocatalyst, adsorbed onto an inert material (catalytic substrate). This enables the accelerated fermentation of critical biomass (such as citrus pulp or sewage sludge), transforming it into a biostabilised and pasteurised material with excellent agronomic properties. All the phosphorus contained in citrus pulp is present in the biostabilised product in organic form, and so is available as a slow-release macro-nutrient.

The process is simple: incoming biomass is mixed with the catalytic substrate. The resulting mixture is turned over periodically (around once a day), promoting vapour escape and good chemical/physical homogenisation, and pushing the biomass on toward the bioreactor outlet. In a few days (around 28 days for pulp and 10 days for sewage sludge), the mixture is biostabilised. The catalytic substrate can easily be separated from the stabilised biomass and fed back into the biomass input. The biostabilised product can be sent for packaging and then on to the biofertiliser market.

The final product complies with all the criteria of the new EU Regulation 2019/1009 for CE marked fertilisers.

Main activity field
Main results

NP-bioTech has numerous advantages. For the company:

  • accelerated and resilient process
  • 100% biomass input, without structuring agent and without dehydration pre-treatment
  • modular plant
  • stabilised and pasteurised product
  • zero waste (absence of leachate)
  • weight reduction up to 90%
  • very low OpEx, certified by the company ≤ 12 €/t
  • saleable product (the product has been registered on the MIPAAF website as Organic soil conditioner for use in organic farming)
  • absence of environmental safeguards for abatement of emissions.

For the environment:

  • absence of polluting emissions
  • energy saving
  • organic fertiliser production certified by UniPi, UniSS and CNR in 2 master's theses.

For the population:

  • no unpleasant smells
  • circular economy.