Poor biodegradability: Mineral oil-based hydraulic fluids are persistent in the environment and can contaminate soil and water sources. They can also pose a fire hazard if spilled or leaked. 

High toxicity: Mineral oil-based hydraulic fluids can cause skin irritation, respiratory problems, and eye damage. They can also harm aquatic life and wildlife if ingested or absorbed. 

Low thermal stability: Mineral oil-based hydraulic fluids can degrade under high temperatures and pressures, forming sludge and varnish that can clog filters and valves. They can also oxidize and produce acidic by-products that can corrode metal components. 

Regulatory pressures and mandates: Many countries and regions have implemented strict regulations and standards for the use and disposal of hydraulic fluids. For example, the European Union has enacted the Eco-Label Regulation, which sets criteria for the biodegradability, toxicity, and renewable content of hydraulic fluids. Similarly, the US Environmental Protection Agency has established the Vessel General Permit, which requires the use of environmentally acceptable lubricants for vessels operating in US waters. 

Consumer demand: Many consumers are becoming more conscious of the environmental footprint of the products and services they purchase. They are looking for companies that adopt green practices and use eco-friendly solutions. This creates a competitive advantage for businesses that use eco-friendly hydraulic fluids and a reputational risk for those that do not. 

Bio-based hydraulic fluids: These are hydraulic fluids that are derived from renewable sources, such as vegetable oils, animal fats, and synthetic esters. They have high biodegradability, low toxicity, and high lubricity. They also have better thermal stability and oxidation resistance than mineral oil-based fluids. However, they can also have some drawbacks, such as higher cost, lower viscosity index, and susceptibility to microbial degradation. 

Water-glycol hydraulic fluids: These are hydraulic fluids that consist of a mixture of water and glycol, a type of alcohol. They have excellent fire resistance, low toxicity, and high biodegradability. They also have good anti-wear and anti-corrosion properties. However, they can also have some disadvantages, such as lower lubricity, higher viscosity, and higher freezing point than mineral oil-based fluids. 

Synthetic hydraulic fluids: These are hydraulic fluids that are made from synthetic compounds, such as polyalphaolefins, polyglycols, and phosphate esters. They have superior performance, such as high viscosity index, high thermal stability, and high oxidation resistance. They also have low toxicity and biodegradability. However, they can also have some drawbacks, such as high cost, low compatibility, and low availability. 

Innovations in additive technology: These are additives that are added to hydraulic fluids to enhance their biodegradability and eco-compatibility. They can also improve other properties, such as anti-wear, anti-foam, and anti-rust. Some examples of eco-friendly additives are zinc-free, ashless, and biodegradable additives. 

Reduced environmental impact: Eco-friendly hydraulic fluids can reduce the risk of soil and water contamination, fire hazard, and harm to aquatic life and wildlife. They can also reduce greenhouse gas emissions and promote the use of renewable resources. 

Improved compliance and reputation: Eco-friendly hydraulic fluids can help users comply with the regulatory requirements and standards for the use and disposal of hydraulic fluids. They can also enhance the reputation and image of the users as environmentally responsible and socially conscious. 

Extended equipment life and reduced maintenance: Eco-friendly hydraulic fluids can improve the performance and reliability of the equipment and components. They can prevent the formation of sludge and varnish, reduce the corrosion and wear of metal parts, and increase the resistance to thermal and oxidative degradation. They can also lower the frequency and cost of maintenance and repairs.