GB/T 39951-2021Evaluation method for degradability of disposable paper products (English PDF)

5.1 Biodegradability test

5.1.1 Reagents and materials

Unless otherwise specified, the reagents used in this Standard refer to analytically-pure reagents. Microbiology reagents shall meet the requirements of microbiology.

5.1.1.1 Water: GB/T 6682, grade three.

5.1.1.2 Trace element solution: the solute concentrations are: boric acid: 500mg/L, potassium iodide: 100mg/L, ferric chloride: 200mg/L, manganese sulfate: 400mg/L, ammonium heptamolybdate: 200mg/L, ferrous sulfate: 400mg/L.

5.1.1.3 Mineral solution: Measure 1mL of calcium chloride solution with a concentration of 0.1g/L, 1mL of sodium chloride solution with a concentration of 0.1g/L, 1mL of trace element solution (5.1.1.2). Weigh 1.0g of potassium dihydrogen phosphate and 0.5g of magnesium sulfate. Use water to set volume to 1000mL.

5.1.1.4 Compost extract: Use the compost produced in the composting device such as organic matter in municipal solid waste, garden and farmland waste to add into water. The mass volume ratio is 1:5. Place for 30min. Use a filter screen with a pore size of about 1mm or a medium-speed qualitative filter paper to filter and remove the residue. Or use a centrifuge to centrifuge at 1000r/min for 15min. Or directly use commercial special inoculants for composting. Prepare according to instructions for use.

5.1.1.5 Inoculum: Measure 500mL of mineral solution (5.1.1.3) and 500mL of compost extract (5.1.1.4). Mix well. Add 10.0g of peptone, 3.0g of beef dipping powder, 5.8g of urea, 20.0g of corn starch, 20.0g of cellulose powder.

5.1.1.6 Reference material: Use thin layer chromatography (TLC) microcrystalline cellulose as a positive control reference material. The particle size is less than 20µm.

5.1.3 Specimen processing

Do not touch the specimen with hands. Wear clean powder-free protective gloves when processing specimens.

Cut the specimen into small pieces of about 10mm×10mm with scissors. Mix well. Use the high-speed crusher (5.1.2.10) to crush the fragments into flocs.

Avoid specimen loss during crushing. Prepare three specimens. The weight of each specimen is within 30g~70g. Try to ensure that each specimen contains an integer number (pieces) of all the components of the specimen. If the mass of a single (piece) specimen is greater than 70g, then take 30g~70g of specimen. Ensure that the specimens taken are representative.

NOTE: Specimens also include powder, granular or other simple shapes.

5.1.4 Test steps

5.1.4.1 Method A: Aerobic composting method

5.1.4.1.1 Determination of total organic carbon content

5.1.4.1.1.1 Total organic carbon content of specimen

According to the instructions for use of the total organic carbon analyzer (5.1.2.9), preheat and calibrate. Prepare another specimen according to 5.1.3.

Use a balance to take 50mg~100mg (depending on the test range and accuracy of the instrument), to the nearest of 0.1mg. Put it into the high temperature resistant specimen cup for testing. Test for 10 times in total. Take the average of 10 test results as the total organic carbon content of the specimen. The result is rounded to 0.0001g/g.

5.1.4.1.1.2 Total organic carbon content of reference material

Refer to 5.1.4.1.1.1 to test the total organic carbon content of the reference material (5.1.1.6). Test twice in total. Take the average value as the total organic carbon content of the reference material. The result is rounded to 0.0001g/g.

5.1.4.1.2 Test preparation stage

5.1.4.1.2.1 Preparation of activated vermiculite

Mix the vermiculite (5.1.1.7) with the inoculum (5.1.1.5) at a ratio of 1:3 (mass: volume). Place it in the vermiculite activation reactor (5.1.2.7). Incubate at (50±2)°C for 3d~4d. […]

5.1.4.1.4 Carbon dioxide emission test

During the test, regularly use the carbon dioxide analysis equipment (5.1.2.6) to measure the carbon dioxide content in the exhaust gas of each compost container. Calculate the cumulative amount of carbon dioxide released. The number of measurements depends on the method used, the accuracy of the required biodegradation curve, and the biodegradability of the specimen. If the measurement method of carbon dioxide analysis instrument is used, measure at least 2 times a day in the biodegradation stage. In the steady phase, measure at least once a day. The gas flow rate at the outlet shall be accurately measured.

If the measurement method of sodium hydroxide absorption and release of carbon dioxide is used, then measure dissolved inorganic carbon once a day in the biological decomposition stage; in the stationary phase, measure 2 times a week.

5.1.4.2 Method B: Component analysis method

For multi-component products, the level of biodegradation of the product shall be calculated based on the level of biodegradation of each component (material). For components with unknown level of biodegradation, then use method A (5.1.4.1) to determine the level of biodegradation of each component.

Calculate the level of biodegradation of the sample according to 5.1.5.2, of which the mass of each component is accurate to 0.001g.

5.1.5 Calculation and presentation of results

5.1.5.1 Calculation of level of biodegradation of aerobic composting

5.1.5.1.1 Level of biodegradation of specimen

Calculate the level of biodegradation of specimen according to formula (1): […]

5.2 Disintegration degree test

5.2.1 Instruments and equipment

5.2.1.1 Compost container

The volume of the compost container shall be large enough (the smallest volume is 140L), so as to ensure that natural heating can occur. The material shall be made of strong, high-temperature resistant, and non-biodegradable materials. Does not affect the composting process or the quality of compost when used.

The bottom layer of the compost container has at least a 5cm thick drip plate to form a drainage system. Use suitable air supply system to provide adequate and continuous ventilation conditions for each compost container.

5.2.1.2 Temperature measuring equipment

The reading is to the nearest of 0.1°C.

5.2.1.3 pH meter

The reading is to the nearest of 0.1 or higher.

5.2.1.4 Oxygen test equipment

The reading is to the nearest of 0.1%.

5.2.1.5 Sieve

Use a test sieve with a suitable shape and 2mm mesh.

5.2.2 Test steps

5.2.2.1 Test preparation stage

5.2.2.1.1 Preparation of biomass waste

Use the used biomass waste as carrier substrate. Try to take samples from the inputs of composting equipment that mainly treats municipal waste. The sample can also be directly sourced from biomass waste from households or grocery stores.

NOTE: The typical artificial biomass waste containing the following ingredients can be selected:

- Fresh fruit and vegetable mixed waste;

- Rabbit feed (seeds and extruded dried vegetable pellets); […]

5.2.2.2.2 Ventilation

Regularly measure the oxygen content of composted materials or the air consumed. Measure at least once every working day during the first month of the test. Conduct once a week thereafter. The oxygen content in the composted material shall be higher than 10%. If the oxygen content is less than 10%, ventilate the biomass waste. The air flow rate per kilogram of total dry solids shall be less than 15L/h.

NOTE: Air flow can control the temperature and moisture content of the compost container.

The air flow to ventilate the compost container shall be consistent with the actual composting equipment. If an excessively high air flow rate is used in practical applications, the amount of ammonia lost with the air can be supplemented by adding some substances (such as urea).

5.2.2.2.3 Moisture content and pH

After turning, take specimens from each test series to measure moisture content and pH. If the moisture content (mass fraction less than 40%) is too low, it will not be conducive to the normal progress of the composting process. Water shall be added at this time.

5.2.2.2.4 Temperature

Measure the temperature in the middle of the compost, at least once every working day.

5.2.2.3 Termination of test

5.2.2.3.1 Cycle

The cultivation cycle is 3 months.

5.2.2.3.2 Residual material

Use a 2mm mesh sieve to sieve all materials. Use running water to wash carefully as much as possible. The washed pellets are dried to constant weight at 105°C (materials with a melting point lower than 105°C is at 40°C). Determine the total dry solids of fragments larger than 2mm.

5.2.3 Calculation

Weigh the mass of the specimen collected in fragments larger than 2mm.

Compare with the mass of the starting specimen (5.2.2.1.2). Calculate the […]

5.4.2 Test methods

When fluorine content is measured, the specimen is calcined in a high-temperature furnace at 1000°C for 15min under the condition of water vapor and oxygen. Collect condensate. Then use ion chromatograph to test. Other elements are tested according to GB/T 30903.

B.1 Simulation of reference culture soil

Any soil that can make seeds germinate and plants grow normally can be used as a reference cultivation soil. No additional fertilizer shall be added to the reference culture soil.

B.2 Sample preparation

Use 50% (mass fraction or volume fraction, stated in the report) compost and reference culture soil to prepare a mixture (sample). The "compost sample" is a mixture of the final product obtained after the disintegration of the specimen and the reference culture soil. The "blank compost" is the reference culture soil without adding the specimen after disintegration.

B.3 Plant species

Use mung bean and wheat in plant species to conduct eco-toxicity test separately.

B.4 Test steps

Take at least 12 trays to test mung bean and wheat separately. Each plant requires 3 to hold compost samples and 3 to hold blank compost. Each tray is filled with at least 200g of sample (B.2). Add at least 100 seeds (B.3) on the upper surface. Use thin layer of inert material to cover seeds, such as silicate sand or perlite. Conduct three sets of parallel tests for each sample. Add water to 70%~100% of the water retention capacity. Regularly replenish the water lost due to evaporation throughout the test period.

NOTE: Tray size is about 30cm×20cm×5cm (length × width × height). During germination, place the tray in a dark place or cover it.

B.5 Result evaluation

Check the number of sprouts of compost samples and blank compost. Use the number value of plant germination to calculate the ratio of the number of sprouts between the compost sample and the blank compost, expressed in percentage. […]

B.6 Validity of results