1 Introduction
Parameter | Value |
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Total weight | 1714 kg |
Effectiveness of weeding process | 65 − 90%1 |
Weeding machinery speed | ~ 2 km/h |
Weeding performance (intended) | 9.6 ha/day |
Operational width | 2 m |
Accuracy of positioning | ± 3 mm |
Interspacing of rows | > 25 cm |
Speed of weeding process (maximum) | ~ 2 km/h |
2 Materials and methods
2.1 Goal and scope of the analysis
2.2 System boundary definition
2.3 Functional unit
2.4 Life cycle inventory
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Autonomous mobile platform
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Weeding implement consisting of three subsystems:
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A laser-based weeding tool including two key components:
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High-power laser source
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Laser targeting unit
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Meristem perception set-up
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Smart central controller
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Component | Description | Weight (kg) |
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Autonomous WeLASER weeder Mobile autonomous platform integrated with the laser weeding implement | 1714 | |
Autonomous mobile platform | 980 | |
Power train, drivetrain | Diesel-electric system: diesel engine, electric generator, batteries, electric engines, gear system, electric components, wheels, and caterpillar | 202 |
Body structure | Chassis, frame, suspension, and auxiliary systems | 778 |
High power laser system implement | 734 | |
Weed-meristem perception | Front Stereo Camera and artificial lighting, recognition RGB cameras, and image recognition computers | 30 |
High-power laser source | High power laser system, DC/DC converters, chillers, collimators | 359 |
Laser targeting system | Enclosure with safety curtains, 4 units of linear axis, scanner heads, visual processing units, and controllers | 300 |
Central controller | Central controller and additional safety components | 45 |
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Average weed density to be removed in the field is 60 weeds per m2 at the 2−4 leaf stage of weeds.
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The four-laser system covers the operational span of 2 m width (3−4 rows of maize, 4 rows of sugar beet, ~15 rows of cereals).
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Average conditions of the field are assumed: flat terrain, good movement conditions, and dry ground.
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The auxiliary process of robot transportation to the fields is included. The WeLASER weeder is owned by a farmer and the distance travel for transportation is 1 km between the field and the farm, assuming that the minimum field area is 1 ha.
2.5 Production phase
Key component | Elements | Material/utility | Weight | Hypothesis on component characterization | Source | |
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Wheels and caterpillar | • Rim wheels, caterpillar | Rim wheels—steel | 3 kg | 108 kg | Characterization based on data on analogous components and literature | (Lagnelöv et al. 2021) |
Caterpillar—rubber | 35 kg | |||||
• Structural elements | Steel components | 70 kg | Ecoinvent v3.8 processes for steel components | |||
Platform body structure | • Chassis, frame, and suspension | Steel | 490 kg | 527 kg | Allocation according to project data and literature, Ecoinvent v3.8 processes used for steel, rubber, and proxy data for High Impact Polystyrene | (Lagnelöv et al. 2021) |
Plastic | 15 kg | |||||
Rubber | 22 kg | |||||
Drivetrain | • Wheel electric motors (2 units) | Electric utility | 25 kg | 50 kg | Project data on motor type and weight, inventory based on literature, adjusted on a weight basis | |
• Gear and transmission | Electric/mechanical utility | 25 kg | Adjusted proxy data on truck components mechanical part—steel, and servomotor (electric utility) 3 kg | (Wolff et al 2020) | ||
Powertrain Diesel-electric system | • Diesel engine 20 kW | Thermal engine | 80 kg | 177 kg | Proxy data for truck diesel engine adjusted on thermal power basis | Engine producer’s specification (Wolff et al. 2020) |
• Electric generator 15 kW | Electric utility | 21 kg | Own estimation based on data on electric engine and alternator, scaled on a weight basis | |||
• Batteries | Li-ion | 15 kg | Ecoinvent v3.8 processes for Li-ion and NaCl batteries | Project data | ||
NaCl | 12.5 10 kg | |||||
• Structural and mechanical components | Steel elements including tank 50 l | 51 kg | Material allocation based on literature, Ecoinvent v3.8 processes for steel components | (Marinescu et al. 2012) | ||
Miscellaneous accessories and systems | • Structural elements three-point hitch, beams, bumpers | Steel | 46 kg | 118 kg | Own estimation, Ecoinvent v3.8 processes for steel components | Project data |
• Smart navigation manager | Electronics: lidar, sensors | 1.2 kg | Literature data adjusted (active—0.6 kg, passive – 0.6 kg components) | (Lagnelöv et al. 2021) | ||
Control and processing unit | 2 kg | Ecoinvent v3.8 process for industrial control unit and mounted wiring board | Project data | |||
Cameras (2 units) | 0.6 kg | Proxy data for general purpose electronic camera | (Hillerström and Troborg 2010) | |||
Steel structure | 4 kg | Ecoinvent v3.8 processes for steel components | Project data | |||
Cables and plugs | 2.2 kg | Ecoinvent v3.8 processes applied for data cables and plugs | Project data | |||
• Electric system | Electric relays | 5 kg | Proxy EcoInvent v3.8 data for industrial control unit | Project data | ||
Structural elements steel | 6 kg | Own estimation, Ecoinvent v3.8 processes for steel components | Project data | |||
Cables and plugs | 26 kg | Scaled truck components inventory, Ecoinvent v3.8 processes for electric cables (21 kg of copper) and plugs | (Nordelöf et al. 2014) | |||
• Electric jack | Electric utility | 15 kg | Scaled and adjusted electric motor inventory | (Nordelöf et al. 2016), product specification | ||
Steel | 10 kg | Ecoinvent v3.8 processes for steel components | ||||
Total weight | 980 |
2.6 Laser implements
Subsystem | Element | Material/utility | Weight | Characterization | Source | |
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Weed meristem perception | • Enclosure and supporting structure | Steel | 15.3 kg | 30.2 kg | Ecoinvent v3.8 processes for non-alloyed steel and aluminum components | Commercial product specifications |
Aluminum | 5.5 kg | |||||
• Image recognition computer | Electronic component | 4 units, 1.58 kg each, 6.3 kg in total | Proxy Ecoinvent v3.8 process for laptop, modified (monitor, HDD and power supply unit excluded) and scaled on weight basis | Project data | ||
Data and network cables | 1 kg | Ecoinvent v3.8 process for data and network cables | Project data | |||
• Recognition cameras stereo RGB | Electronic component | 4 units, 0.15 kg each, 0.6 kg in total | Proxy data for general purpose electronic camera | (Hillerström and Troborg 2010) | ||
• Front camera stereo RGB | Electronic component | 0.3 kg | ||||
• Artificial lighting | Lighting utility | 10 units, 0.12 kg, 1.2 kg in total | Literature data on lighting adapted and Ecoinvent v3.8 data | (Casamayor et al. 2018) | ||
Laser targeting | • Laser scanners | Control units | 3.6 kg (4 units) | 85.2 kg | Estimation, proxy Ecoinvent v3.8 process for control unit electronics | Electronics’ specifications |
Graphics data processing unit | 6.6 kg (4 units) | Ecoinvent v3.8 process for PC computer, modified (HDD and power unit excluded, wiring board and integrated circuit included) | Commercial product' specification | |||
Scanner head | 21.8 (4 units) | Own characterization of scanner head including servomotors and optics | Producers’ technical information | |||
Optic system—aluminum, glass, graphite | 10.6 kg (4 units) | Own characterization based on analogous components | Producer’ technical information | |||
Cables and plugs, switches, jacks, connectors | 10 kg (4 units) | Ecoinvent v3.8 data on cables, connectors and plugs (5.5 kg), switches and jacks (4.5 kg) | Project data | |||
Enclosure (aluminum) and ventilator | 11 kg (4 units) | Ecoinvent v3.8 processes for aluminum product, ventilators 0.8 kg | Project data, example of ventilator EPD for commercial product | |||
• Linear axis | Aluminum runner and axis | 10 kg (4 units) | Own estimation, Ecoinvent v3.8 processes for aluminum components | Commercial products’ data | ||
Servomotor and electric gear utilities | 8 kg (4 units) | Own characterization of electric utilities based on products' technical characteristics | ||||
Caterpillar neoprene, aluminum | 3.6 kg (4 units) | Estimated, Ecoinvent v3.8 processes for aluminum (0.9 kg) components and rubber (2.7 kg) | Commercial products’ data | |||
Enclosure with safety curtains | • Structural elements | Aluminum frame | 40 kg | 215 kg | Estimation based on products' technical characteristics, Ecoinvent v3.8 processes for aluminum, steel, and rubber components | Commercial products’ data |
Steel plates | 170 kg | |||||
Double safety flaps (rubber) | 5 kg | |||||
Control Management | • Central controller | Controller including communications, sensors, and ventilation | 15 kg | 45 kg | Proxy Ecoinvent v3.8 data for industrial controller electronics for communication Wifi/5 g router (0.23 kg), sensors (0.6 kg), ventilation (0.3 kg) | Commercial products’specification (Lagnelöv et al. 2021) |
• Enclosure | Steel structure | 5.4 kg | Estimated, based on rack' technical description | Project data, commercial product' data | ||
Aluminum | 1.6 kg | |||||
• Fibers and cables | Electric, data, and network cables | 18 kg in total | Ecoinvent v3.8 process for coated copper cables, data, and network cables | |||
Project data | ||||||
• Additional safety components | Safety controller | 5 kg | Proxy Ecoinvent v3.8 process for industrial controller electronics | |||
Own characterization on ventilation, power system and enclosure based on products’ technical information | Commercial products’ information | |||||
High power laser source | • DC/DC converters | Electric/electronic utility | 4 units, 5.6 kg each, 22.4 kg in total | 359.4 kg | Proxy Ecoinvent v3.8 process for electric car converter | Project data |
• Thulium laser high power sources | Power supply | 5.2 kg | Ecoinvent v3.8 process for transformer | Commercial lasers technical information (Fuhrberg et al. 2020) | ||
Fibers | 1 kg | Proxy Ecoinvent v3.8 process for glass fiber | ||||
6 laser diodes | 12 kg | Estimation based on products technical characteristics | ||||
Control unit, electronics | 8 kg | Estimation, proxy Ecoinvent v3.8 processes for industrial control unit and wiring board | ||||
Cables, fiber connectors, collimators | 13 kg | Estimation, Ecoinvent v3.8 processes for network, data and electric cables, collimators (steel, aluminum and glass) | ||||
Chassis for electronics | 16 kg | Estimation, Ecoinvent v3.8 process for chassis for network unit | ||||
Steel structure | 56 kg | Estimation, Ecoinvent v3.8 processes for steel component | ||||
• Chillers | Cooling equipment | 4 units, 42 kg each, 172 kg in total | Own model based on producers’ specifications | (Rossi et al. 2021) and commercial product EPD data | ||
• Rack cabinets (two units) | Steel structure | 39,5 kg | Ecoinvent v3.8 processes for non-alloyed steel and aluminum | Commercial product specification | ||
Aluminum | 14,2 kg | |||||
Implement total | 734.7 kg |
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On the mobile platform, the key electronic components: high-power laser source, computers, weed recognition subsystem, central control subsystem, and chillers are positioned.
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The weeding implement is mounted on the tow, including the laser scanners, cameras, and laser targeting subsystem.
2.7 Use phase characterization
Parameter | Unit | Value | Range | Source of information/comments |
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Time of operation of each laser | s | 0.04 | 0.08 − 0.04 | WeLASER projecta |
Laser optical power | W | 500 | 250 − 500 | WeLASER project |
Power of each laser system | kW | 3.6 | 1.8 − 3.6 | WeLASER project |
Laser optic energy used per weed meristem | J per weed | 20 | 5 – 20 | |
Electric energy of high-power laser | J per weed | 133 | 66 − 133 | WeLASER project |
Thermal energy demand for high power laser operations | J per weed | 462 | 229 − 462 | Own calculations based on electric-diesel engine efficiency—baseline case |
Energy per treated area | J mm2 | 63 | 16 − 63 | 2 mm beam diameter |
Weed meristem perception subsystem power | W | 522 | - | WeLASER project |
Laser targeting subsystem power | W | 1104 | - | WeLASER project |
Central controller power | W | 650 | - | WeLASER project |
Diesel engine power | kW | 20 | 19 − 21 | WeLASER project, adjusted value |
Specific fuel consumption | g of fuel kWh−1 | 250 | 230 − 300 | |
Heat value of diesel oil | MJ l−1 | 38 | 35.8 − 38.6 | Energy Efficiency & Renewable Energyb (Eriksson and Ahlgren 2013) |
Diesel oil density | kg l−1 | 0.85 | 0.82–0.85 | (Schaschke et al. 2013; Kohler enginesc) |
Electric generator | kW | 15 | 14 − 16 | Project data for specific engine type |
Time of operation of the robot | hours hectare−1 | 2,5 | 1.2 − 5 | Depending on the variance of weeds density, their statistical distribution and energy availability |
Time of laser operation | hours hectare−1 | 1.7 | 0.14 − 5 | WeLASER project |
Time of standby operation | hours hectare−1 | 0.8 | 0.6 − 1.2 | Own calculation based on WeLASER project data |
Density of weeds (average) | Weeds m−2 | 60 | 5–120 (180) | |
Number of lasers | number | 4 | - | WeLASER project |
Width of operation | M | 2 | - | WeLASER project |
Robot operational velocity | km h−1 | 2 | 1 − 4 | WeLASER project |
Fuel consumption per ha | l ha−1 | 14.6 | 10.7 − 28.3 | |
Fuel allocated to weeder's traction per ha | l ha−1 | 5 | 4 − 7 | |
Fuel allocated to laser implement per ha | l ha−1 | 9.6 | 6.7 − 21.3 | WeLASER project data and components characterization, values depend on the variance of weeds density, their statistical distribution and energy availability |
Thermal efficiency of the diesel engine | % | 32 | 30 − 35 |
Components | Thermal energy required for component operation (MJ ha−1) | ||
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5 plants m−2 | 60 plants m−2 | 120 plants m−2 | |
Mobile platform | 190a | 190 | 190 |
The laser implement total | 58.8 | 363.6 | 700.9 |
Weed-meristem perception | 7.8 | 16.3 | 21.8 |
Laser targeting system | 1.9 | 23.0 | 46.0 |
Central controller including additional safety components (safety controller and sensors) | 12.9 | 20.3 | 27.1 |
High-power laser source including chiller and DC/DC converter | 36.2 | 304 | 606 |
Total WeLASER weeder maximum engine power | 248.8b | 553.63c | 890.94d |
Parameter/process | WeLASER weeder subsystems | ||||
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High-power laser source | Meristem targeting | Weed meristem perception | Control system | Mobile platform | |
Expected lifetime | 5000 as minimum 25,000 on average–50,000 working hours (project expert information) | 10 years for industrial scanners (proxy dataa) | 10,000 working hours, industrial computer 5 − 15 yearsb 6 − 10 years for industrial camerasc | Industrial computer 5 − 15 yearsb | |
Maintenance | Spare parts (not specified) | Specialized liquids, spare parts, and other materials not specified | Cleaning agents, spare parts not specified | Spare parts not specified | Lubricants 74 kg and rubber parts 55 kg, electric energy 2531 MJ in 10 year lifetime according to (Lagnelöv et al. 2021). Spare parts and hydraulic oil are not included—engine oil calculated based on oil consumption 0.013 l/h (engine’ producer data) |
2.8 Disposal phase characterization
Material/process | High-power laser source | Meristem targeting | Weed meristem perception | Control system | Mobile platform |
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Opportunity for reusing of the components | Yes | Yes | Yes | Yes | Yesa |
Medium rate of material reuse/recyclingb | 71% | 86% | 86% | 37% | 80% |
Landfillingb | 16% | 7% | 8% | 45% | 5% |
Incineratingb | 13% | 7% | 6% | 18% | 15% |
2.9 Interpretation of the results
2.9.1 Sensitivity analysis and data uncertainty
Parameter | Tested parameters |
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Lifetime of the components | 3000 − 20,000 working hours |
Transport of the vehicle for farms/farms area | 1–50 km, range of farms’ cultivated area 1–100 ha |
Energy required for plant meristem destruction at fixed speed of 2 km h−1 | 5–20 J plant−1 (meristem) |
Density of weeds m−2 at a fixed speed of 2 km h−1 | 5–120 weeds m−2 |
3 Results and discussion
3.1 Environmental impacts in the WeLASER weeder life cycle
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human toxicity
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climate change human health
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climate change ecosystem
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climate change ecosystem
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fossil depletion
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metal depletion
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particulate matter
3.2 WeLASER production phase
3.3 The mobile platform
3.4 The WeLASER implement (laser-based weeding tool)
3.5 The WeLASER weeder use phase
3.6 The WeLASER weeder dismantling and disposal
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basic construction components and materials including steel and copper, which have a relatively high potential for reuse and recycling (rates above 85% up to 100%).
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electronic components which currently pose challenges for reuse for which a lower recovery rate was assigned.
3.7 The weeding techniques comparison
3.8 Sensitivity analysis
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The operational settings, speed, weeds density, variance of terrain and environmental conditions.
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The final performance of the design, energy consumption and weeding efficiency of the WeLASER weeder (expected efficiency of 60–90%).
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The transportation requirements for the WeLASER weeder as it requires supporting transport.